signals: use an alias for the boost::signals2 namespace

diff --git a/src/btcsignals.h b/src/btcsignals.h
index 816d9125..415d8b86 100644
--- a/src/btcsignals.h
+++ b/src/btcsignals.h
@@ -9,4 +9,6 @@
 #include <boost/signals2/optional_last_value.hpp>
 #include <boost/signals2/signal.hpp>
 
+namespace btcsignals = boost::signals2;
+
 #endif // BITCOIN_BTCSIGNALS_H
diff --git a/src/common/interfaces.cpp b/src/common/interfaces.cpp
index dc98fac6..de028f9c 100644
--- a/src/common/interfaces.cpp
+++ b/src/common/interfaces.cpp
@@ -23,11 +23,11 @@ public:
 class SignalHandler : public interfaces::Handler
 {
 public:
-    explicit SignalHandler(boost::signals2::connection connection) : m_connection(std::move(connection)) {}
+    explicit SignalHandler(btcsignals::connection connection) : m_connection(std::move(connection)) {}
 
     void disconnect() override { m_connection.disconnect(); }
 
-    boost::signals2::scoped_connection m_connection;
+    btcsignals::scoped_connection m_connection;
 };
 
 class EchoImpl : public interfaces::Echo
@@ -44,7 +44,7 @@ std::unique_ptr<Handler> MakeCleanupHandler(std::function<void()> cleanup)
     return std::make_unique<common::CleanupHandler>(std::move(cleanup));
 }
 
-std::unique_ptr<Handler> MakeSignalHandler(boost::signals2::connection connection)
+std::unique_ptr<Handler> MakeSignalHandler(btcsignals::connection connection)
 {
     return std::make_unique<common::SignalHandler>(std::move(connection));
 }
diff --git a/src/interfaces/handler.h b/src/interfaces/handler.h
index 5de131ee..09c23638 100644
--- a/src/interfaces/handler.h
+++ b/src/interfaces/handler.h
@@ -24,8 +24,8 @@ public:
     virtual void disconnect() = 0;
 };
 
-//! Return handler wrapping a boost signal connection.
-std::unique_ptr<Handler> MakeSignalHandler(boost::signals2::connection connection);
+//! Return handler wrapping a btcsignals connection.
+std::unique_ptr<Handler> MakeSignalHandler(btcsignals::connection connection);
 
 //! Return handler wrapping a cleanup function.
 std::unique_ptr<Handler> MakeCleanupHandler(std::function<void()> cleanup);
diff --git a/src/node/interface_ui.cpp b/src/node/interface_ui.cpp
index 525d341e..6b1fe72f 100644
--- a/src/node/interface_ui.cpp
+++ b/src/node/interface_ui.cpp
@@ -13,22 +13,22 @@ using util::MakeUnorderedList;
 CClientUIInterface uiInterface;
 
 struct UISignals {
-    boost::signals2::signal<CClientUIInterface::ThreadSafeMessageBoxSig, boost::signals2::optional_last_value<bool>> ThreadSafeMessageBox;
-    boost::signals2::signal<CClientUIInterface::ThreadSafeQuestionSig, boost::signals2::optional_last_value<bool>> ThreadSafeQuestion;
-    boost::signals2::signal<CClientUIInterface::InitMessageSig> InitMessage;
-    boost::signals2::signal<CClientUIInterface::InitWalletSig> InitWallet;
-    boost::signals2::signal<CClientUIInterface::NotifyNumConnectionsChangedSig> NotifyNumConnectionsChanged;
-    boost::signals2::signal<CClientUIInterface::NotifyNetworkActiveChangedSig> NotifyNetworkActiveChanged;
-    boost::signals2::signal<CClientUIInterface::NotifyAlertChangedSig> NotifyAlertChanged;
-    boost::signals2::signal<CClientUIInterface::ShowProgressSig> ShowProgress;
-    boost::signals2::signal<CClientUIInterface::NotifyBlockTipSig> NotifyBlockTip;
-    boost::signals2::signal<CClientUIInterface::NotifyHeaderTipSig> NotifyHeaderTip;
-    boost::signals2::signal<CClientUIInterface::BannedListChangedSig> BannedListChanged;
+    btcsignals::signal<CClientUIInterface::ThreadSafeMessageBoxSig, btcsignals::optional_last_value<bool>> ThreadSafeMessageBox;
+    btcsignals::signal<CClientUIInterface::ThreadSafeQuestionSig, btcsignals::optional_last_value<bool>> ThreadSafeQuestion;
+    btcsignals::signal<CClientUIInterface::InitMessageSig> InitMessage;
+    btcsignals::signal<CClientUIInterface::InitWalletSig> InitWallet;
+    btcsignals::signal<CClientUIInterface::NotifyNumConnectionsChangedSig> NotifyNumConnectionsChanged;
+    btcsignals::signal<CClientUIInterface::NotifyNetworkActiveChangedSig> NotifyNetworkActiveChanged;
+    btcsignals::signal<CClientUIInterface::NotifyAlertChangedSig> NotifyAlertChanged;
+    btcsignals::signal<CClientUIInterface::ShowProgressSig> ShowProgress;
+    btcsignals::signal<CClientUIInterface::NotifyBlockTipSig> NotifyBlockTip;
+    btcsignals::signal<CClientUIInterface::NotifyHeaderTipSig> NotifyHeaderTip;
+    btcsignals::signal<CClientUIInterface::BannedListChangedSig> BannedListChanged;
 };
 static UISignals g_ui_signals;
 
 #define ADD_SIGNALS_IMPL_WRAPPER(signal_name)                                                                 \
-    boost::signals2::connection CClientUIInterface::signal_name##_connect(std::function<signal_name##Sig> fn) \
+    btcsignals::connection CClientUIInterface::signal_name##_connect(std::function<signal_name##Sig> fn) \
     {                                                                                                         \
         return g_ui_signals.signal_name.connect(fn);                                                          \
     }
diff --git a/src/node/interface_ui.h b/src/node/interface_ui.h
index 8c90bdf4..c33df59a 100644
--- a/src/node/interface_ui.h
+++ b/src/node/interface_ui.h
@@ -67,7 +67,7 @@ public:
 #define ADD_SIGNALS_DECL_WRAPPER(signal_name, rtype, ...)                                  \
     rtype signal_name(__VA_ARGS__);                                                        \
     using signal_name##Sig = rtype(__VA_ARGS__);                                           \
-    boost::signals2::connection signal_name##_connect(std::function<signal_name##Sig> fn)
+    btcsignals::connection signal_name##_connect(std::function<signal_name##Sig> fn)
 
     /** Show message box. */
     ADD_SIGNALS_DECL_WRAPPER(ThreadSafeMessageBox, bool, const bilingual_str& message, unsigned int style);
diff --git a/src/noui.cpp b/src/noui.cpp
index af04cb00..6f33b227 100644
--- a/src/noui.cpp
+++ b/src/noui.cpp
@@ -13,9 +13,9 @@
 #include <string>
 
 /** Store connections so we can disconnect them when suppressing output */
-boost::signals2::connection noui_ThreadSafeMessageBoxConn;
-boost::signals2::connection noui_ThreadSafeQuestionConn;
-boost::signals2::connection noui_InitMessageConn;
+btcsignals::connection noui_ThreadSafeMessageBoxConn;
+btcsignals::connection noui_ThreadSafeQuestionConn;
+btcsignals::connection noui_InitMessageConn;
 
 bool noui_ThreadSafeMessageBox(const bilingual_str& message, unsigned int style)
 {
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index cb236bd7..0b89c605 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -485,9 +485,9 @@ int GuiMain(int argc, char* argv[])
     util::ThreadSetInternalName("main");
 
     // Subscribe to global signals from core
-    boost::signals2::scoped_connection handler_message_box = ::uiInterface.ThreadSafeMessageBox_connect(noui_ThreadSafeMessageBox);
-    boost::signals2::scoped_connection handler_question = ::uiInterface.ThreadSafeQuestion_connect(noui_ThreadSafeQuestion);
-    boost::signals2::scoped_connection handler_init_message = ::uiInterface.InitMessage_connect(noui_InitMessage);
+    btcsignals::scoped_connection handler_message_box = ::uiInterface.ThreadSafeMessageBox_connect(noui_ThreadSafeMessageBox);
+    btcsignals::scoped_connection handler_question = ::uiInterface.ThreadSafeQuestion_connect(noui_ThreadSafeQuestion);
+    btcsignals::scoped_connection handler_init_message = ::uiInterface.InitMessage_connect(noui_InitMessage);
 
     // Do not refer to data directory yet, this can be overridden by Intro::pickDataDirectory
 
diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index b62b2a3b..4369a078 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -87,7 +87,7 @@ Txid SendCoins(CWallet& wallet, SendCoinsDialog& sendCoinsDialog, const CTxDesti
         ->findChild<QCheckBox*>("optInRBF")
         ->setCheckState(rbf ? Qt::Checked : Qt::Unchecked);
     Txid txid;
-    boost::signals2::scoped_connection c(wallet.NotifyTransactionChanged.connect([&txid](const Txid& hash, ChangeType status) {
+    btcsignals::scoped_connection c(wallet.NotifyTransactionChanged.connect([&txid](const Txid& hash, ChangeType status) {
         if (status == CT_NEW) txid = hash;
     }));
     ConfirmSend(/*text=*/nullptr, confirm_type);
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index 8647ae48..f6eb9cd3 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -155,10 +155,10 @@ public:
     };
 
     /** Keypool has new keys */
-    boost::signals2::signal<void ()> NotifyCanGetAddressesChanged;
+    btcsignals::signal<void ()> NotifyCanGetAddressesChanged;
 
     /** Birth time changed */
-    boost::signals2::signal<void (const ScriptPubKeyMan* spkm, int64_t new_birth_time)> NotifyFirstKeyTimeChanged;
+    btcsignals::signal<void (const ScriptPubKeyMan* spkm, int64_t new_birth_time)> NotifyFirstKeyTimeChanged;
 };
 
 /** OutputTypes supported by the LegacyScriptPubKeyMan */
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index a46a6455..7d14ecff 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -826,13 +826,13 @@ public:
     void Close();
 
     /** Wallet is about to be unloaded */
-    boost::signals2::signal<void ()> NotifyUnload;
+    btcsignals::signal<void ()> NotifyUnload;
 
     /**
      * Address book entry changed.
      * @note called without lock cs_wallet held.
      */
-    boost::signals2::signal<void(const CTxDestination& address,
+    btcsignals::signal<void(const CTxDestination& address,
                                  const std::string& label, bool isMine,
                                  AddressPurpose purpose, ChangeType status)>
         NotifyAddressBookChanged;
@@ -841,19 +841,19 @@ public:
      * Wallet transaction added, removed or updated.
      * @note called with lock cs_wallet held.
      */
-    boost::signals2::signal<void(const Txid& hashTx, ChangeType status)> NotifyTransactionChanged;
+    btcsignals::signal<void(const Txid& hashTx, ChangeType status)> NotifyTransactionChanged;
 
     /** Show progress e.g. for rescan */
-    boost::signals2::signal<void (const std::string &title, int nProgress)> ShowProgress;
+    btcsignals::signal<void (const std::string &title, int nProgress)> ShowProgress;
 
     /** Keypool has new keys */
-    boost::signals2::signal<void ()> NotifyCanGetAddressesChanged;
+    btcsignals::signal<void ()> NotifyCanGetAddressesChanged;
 
     /**
      * Wallet status (encrypted, locked) changed.
      * Note: Called without locks held.
      */
-    boost::signals2::signal<void (CWallet* wallet)> NotifyStatusChanged;
+    btcsignals::signal<void (CWallet* wallet)> NotifyStatusChanged;
 
     /** Inquire whether this wallet broadcasts transactions. */
     bool GetBroadcastTransactions() const { return fBroadcastTransactions; }