autotools: Rename `build-aux` to `autotools-aux`

diff --git a/.gitignore b/.gitignore
index ce33a84..cae2821 100644
--- a/.gitignore
+++ b/.gitignore
@@ -45,20 +45,9 @@ coverage.*.html
 *.gcno
 *.gcov
 
-build-aux/ar-lib
-build-aux/config.guess
-build-aux/config.sub
-build-aux/depcomp
-build-aux/install-sh
-build-aux/ltmain.sh
-build-aux/m4/libtool.m4
-build-aux/m4/lt~obsolete.m4
-build-aux/m4/ltoptions.m4
-build-aux/m4/ltsugar.m4
-build-aux/m4/ltversion.m4
-build-aux/missing
-build-aux/compile
-build-aux/test-driver
+/autotools-aux/
+!/autotools-aux/m4/bitcoin_secp.m4
+
 libsecp256k1.pc
 
 ### CMake
diff --git a/Makefile.am b/Makefile.am
index dc79857..07d7a2b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,4 +1,4 @@
-ACLOCAL_AMFLAGS = -I build-aux/m4
+ACLOCAL_AMFLAGS = -I autotools-aux/m4
 
 # AM_CFLAGS will be automatically prepended to CFLAGS by Automake when compiling some foo
 # which does not have an explicit foo_CFLAGS variable set.
diff --git a/autotools-aux/m4/bitcoin_secp.m4 b/autotools-aux/m4/bitcoin_secp.m4
new file mode 100644
index 0000000..1428d4d
--- /dev/null
+++ b/autotools-aux/m4/bitcoin_secp.m4
@@ -0,0 +1,91 @@
+dnl escape "$0x" below using the m4 quadrigaph @S|@, and escape it again with a \ for the shell.
+AC_DEFUN([SECP_X86_64_ASM_CHECK],[
+AC_MSG_CHECKING(for x86_64 assembly availability)
+AC_LINK_IFELSE([AC_LANG_PROGRAM([[
+  #include <stdint.h>]],[[
+  uint64_t a = 11, tmp = 0;
+  __asm__ __volatile__("movq \@S|@0x100000000,%1; mulq %%rsi" : "+a"(a) : "S"(tmp) : "cc", "%rdx");
+  ]])], [has_x86_64_asm=yes], [has_x86_64_asm=no])
+AC_MSG_RESULT([$has_x86_64_asm])
+])
+
+AC_DEFUN([SECP_ARM32_ASM_CHECK], [
+  AC_MSG_CHECKING(for ARM32 assembly availability)
+  SECP_ARM32_ASM_CHECK_CFLAGS_saved_CFLAGS="$CFLAGS"
+  CFLAGS="-x assembler"
+  AC_LINK_IFELSE([AC_LANG_SOURCE([[
+    .syntax unified
+    .eabi_attribute 24, 1
+    .eabi_attribute 25, 1
+    .text
+    .global main
+    main:
+      ldr r0, =0x002A
+      mov r7, #1
+      swi 0   
+    ]])], [has_arm32_asm=yes], [has_arm32_asm=no])
+  AC_MSG_RESULT([$has_arm32_asm])
+  CFLAGS="$SECP_ARM32_ASM_CHECK_CFLAGS_saved_CFLAGS"
+])
+
+AC_DEFUN([SECP_VALGRIND_CHECK],[
+AC_MSG_CHECKING([for valgrind support])
+if test x"$has_valgrind" != x"yes"; then
+  CPPFLAGS_TEMP="$CPPFLAGS"
+  CPPFLAGS="$VALGRIND_CPPFLAGS $CPPFLAGS"
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+    #include <valgrind/memcheck.h>
+  ]], [[
+    #if defined(NVALGRIND)
+    #  error "Valgrind does not support this platform."
+    #endif
+  ]])], [has_valgrind=yes])
+  CPPFLAGS="$CPPFLAGS_TEMP"
+fi
+AC_MSG_RESULT($has_valgrind)
+])
+
+AC_DEFUN([SECP_MSAN_CHECK], [
+AC_MSG_CHECKING(whether MemorySanitizer is enabled)
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+  #if defined(__has_feature)
+  #  if __has_feature(memory_sanitizer)
+       /* MemorySanitizer is enabled. */
+  #  elif
+  #    error "MemorySanitizer is disabled."
+  #  endif
+  #else
+  #  error "__has_feature is not defined."
+  #endif
+  ]])], [msan_enabled=yes], [msan_enabled=no])
+AC_MSG_RESULT([$msan_enabled])
+])
+
+dnl SECP_TRY_APPEND_CFLAGS(flags, VAR)
+dnl Append flags to VAR if CC accepts them.
+AC_DEFUN([SECP_TRY_APPEND_CFLAGS], [
+  AC_MSG_CHECKING([if ${CC} supports $1])
+  SECP_TRY_APPEND_CFLAGS_saved_CFLAGS="$CFLAGS"
+  CFLAGS="$1 $CFLAGS"
+  AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])], [flag_works=yes], [flag_works=no])
+  AC_MSG_RESULT($flag_works)
+  CFLAGS="$SECP_TRY_APPEND_CFLAGS_saved_CFLAGS"
+  if test x"$flag_works" = x"yes"; then
+    $2="$$2 $1"
+  fi
+  unset flag_works
+  AC_SUBST($2)
+])
+
+dnl SECP_SET_DEFAULT(VAR, default, default-dev-mode)
+dnl Set VAR to default or default-dev-mode, depending on whether dev mode is enabled
+AC_DEFUN([SECP_SET_DEFAULT], [
+  if test "${enable_dev_mode+set}" != set; then
+    AC_MSG_ERROR([[Set enable_dev_mode before calling SECP_SET_DEFAULT]])
+  fi
+  if test x"$enable_dev_mode" = x"yes"; then
+    $1="$3"
+  else
+    $1="$2"
+  fi
+])
diff --git a/build-aux/m4/bitcoin_secp.m4 b/build-aux/m4/bitcoin_secp.m4
deleted file mode 100644
index 1428d4d..0000000
--- a/build-aux/m4/bitcoin_secp.m4
+++ /dev/null
@@ -1,91 +0,0 @@
-dnl escape "$0x" below using the m4 quadrigaph @S|@, and escape it again with a \ for the shell.
-AC_DEFUN([SECP_X86_64_ASM_CHECK],[
-AC_MSG_CHECKING(for x86_64 assembly availability)
-AC_LINK_IFELSE([AC_LANG_PROGRAM([[
-  #include <stdint.h>]],[[
-  uint64_t a = 11, tmp = 0;
-  __asm__ __volatile__("movq \@S|@0x100000000,%1; mulq %%rsi" : "+a"(a) : "S"(tmp) : "cc", "%rdx");
-  ]])], [has_x86_64_asm=yes], [has_x86_64_asm=no])
-AC_MSG_RESULT([$has_x86_64_asm])
-])
-
-AC_DEFUN([SECP_ARM32_ASM_CHECK], [
-  AC_MSG_CHECKING(for ARM32 assembly availability)
-  SECP_ARM32_ASM_CHECK_CFLAGS_saved_CFLAGS="$CFLAGS"
-  CFLAGS="-x assembler"
-  AC_LINK_IFELSE([AC_LANG_SOURCE([[
-    .syntax unified
-    .eabi_attribute 24, 1
-    .eabi_attribute 25, 1
-    .text
-    .global main
-    main:
-      ldr r0, =0x002A
-      mov r7, #1
-      swi 0   
-    ]])], [has_arm32_asm=yes], [has_arm32_asm=no])
-  AC_MSG_RESULT([$has_arm32_asm])
-  CFLAGS="$SECP_ARM32_ASM_CHECK_CFLAGS_saved_CFLAGS"
-])
-
-AC_DEFUN([SECP_VALGRIND_CHECK],[
-AC_MSG_CHECKING([for valgrind support])
-if test x"$has_valgrind" != x"yes"; then
-  CPPFLAGS_TEMP="$CPPFLAGS"
-  CPPFLAGS="$VALGRIND_CPPFLAGS $CPPFLAGS"
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-    #include <valgrind/memcheck.h>
-  ]], [[
-    #if defined(NVALGRIND)
-    #  error "Valgrind does not support this platform."
-    #endif
-  ]])], [has_valgrind=yes])
-  CPPFLAGS="$CPPFLAGS_TEMP"
-fi
-AC_MSG_RESULT($has_valgrind)
-])
-
-AC_DEFUN([SECP_MSAN_CHECK], [
-AC_MSG_CHECKING(whether MemorySanitizer is enabled)
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
-  #if defined(__has_feature)
-  #  if __has_feature(memory_sanitizer)
-       /* MemorySanitizer is enabled. */
-  #  elif
-  #    error "MemorySanitizer is disabled."
-  #  endif
-  #else
-  #  error "__has_feature is not defined."
-  #endif
-  ]])], [msan_enabled=yes], [msan_enabled=no])
-AC_MSG_RESULT([$msan_enabled])
-])
-
-dnl SECP_TRY_APPEND_CFLAGS(flags, VAR)
-dnl Append flags to VAR if CC accepts them.
-AC_DEFUN([SECP_TRY_APPEND_CFLAGS], [
-  AC_MSG_CHECKING([if ${CC} supports $1])
-  SECP_TRY_APPEND_CFLAGS_saved_CFLAGS="$CFLAGS"
-  CFLAGS="$1 $CFLAGS"
-  AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])], [flag_works=yes], [flag_works=no])
-  AC_MSG_RESULT($flag_works)
-  CFLAGS="$SECP_TRY_APPEND_CFLAGS_saved_CFLAGS"
-  if test x"$flag_works" = x"yes"; then
-    $2="$$2 $1"
-  fi
-  unset flag_works
-  AC_SUBST($2)
-])
-
-dnl SECP_SET_DEFAULT(VAR, default, default-dev-mode)
-dnl Set VAR to default or default-dev-mode, depending on whether dev mode is enabled
-AC_DEFUN([SECP_SET_DEFAULT], [
-  if test "${enable_dev_mode+set}" != set; then
-    AC_MSG_ERROR([[Set enable_dev_mode before calling SECP_SET_DEFAULT]])
-  fi
-  if test x"$enable_dev_mode" = x"yes"; then
-    $1="$3"
-  else
-    $1="$2"
-  fi
-])
diff --git a/configure.ac b/configure.ac
index 6028ee2..36699c1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -19,8 +19,8 @@ define(_LIB_VERSION_AGE, 0)
 
 AC_INIT([libsecp256k1],m4_join([.], _PKG_VERSION_MAJOR, _PKG_VERSION_MINOR, _PKG_VERSION_PATCH)m4_if(_PKG_VERSION_IS_RELEASE, [true], [], [-dev]),[https://github.com/bitcoin-core/secp256k1/issues],[libsecp256k1],[https://github.com/bitcoin-core/secp256k1])
 
-AC_CONFIG_AUX_DIR([build-aux])
-AC_CONFIG_MACRO_DIR([build-aux/m4])
+AC_CONFIG_AUX_DIR([autotools-aux])
+AC_CONFIG_MACRO_DIR([autotools-aux/m4])
 AC_CANONICAL_HOST
 
 # Require Automake 1.11.2 for AM_PROG_AR
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ecbbbbe..46db778 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -95,7 +95,7 @@ set_target_properties(secp256k1_objs PROPERTIES
 )
 
 # This emulates Libtool to make sure Libtool and CMake agree on the ABI version,
-# see below "Calculate the version variables" in build-aux/ltmain.sh.
+# see below "Calculate the version variables" in autotools-aux/ltmain.sh.
 math(EXPR ${PROJECT_NAME}_soversion "${${PROJECT_NAME}_LIB_VERSION_CURRENT} - ${${PROJECT_NAME}_LIB_VERSION_AGE}")
 set_target_properties(secp256k1 PROPERTIES
   SOVERSION ${${PROJECT_NAME}_soversion}