Use new minimal boost_asio_core dependency.

Re-enable Boost.Asio in 32-bit MinGW-w64 job in AppVeyor.

CMakeLists.txt

@@ -527,7 +527,7 @@ endif()
 if (NOT BOOST_LOG_WITHOUT_ASIO)
     target_link_libraries(boost_log
         PRIVATE
-            Boost::asio
+            Boost::asio_core
     )
 endif()
 
@@ -654,7 +654,7 @@ if (NOT BOOST_LOG_WITHOUT_SETTINGS_PARSERS)
     if (NOT BOOST_LOG_WITHOUT_ASIO)
         target_link_libraries(boost_log_setup
             PRIVATE
-                Boost::asio
+                Boost::asio_core
         )
     endif()
 

appveyor.yml

@@ -72,9 +72,6 @@ environment:
       ADDRESS_MODEL: 32
       CXXSTD: 11,14
       ADDPATH: C:\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\bin
-      # Boost.Context, on which Boost.ASIO depends, does not build on this target, which prevents Boost.Log from building.
-      # https://github.com/chriskohlhoff/asio/issues/1637
-      B2_ARGS: define=BOOST_LOG_WITHOUT_ASIO=1
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
     - TOOLSET: clang-win
       ADDRESS_MODEL: 32

build/log-build-config.jam

@@ -131,7 +131,7 @@ rule check-asio ( properties * )
 
     if ! [ has-config-flag BOOST_LOG_WITHOUT_ASIO : $(properties) ]
     {
-        result = <library>/boost/asio//boost_asio ;
+        result = <library>/boost/asio//boost_asio_core ;
     }
 
     return $(result) ;

doc/log.qbk

@@ -45,7 +45,7 @@
 [def __boost_scope_exit__ [@https://www.boost.org/doc/libs/release/libs/scope_exit/doc/html/index.html Boost.ScopeExit]]
 [def __boost_any__ [@https://www.boost.org/doc/libs/release/doc/html/any.html Boost.Any]]
 [def __boost_property_tree__ [@https://www.boost.org/doc/libs/release/doc/html/property_tree.html Boost.PropertyTree]]
-[def __boost_asio__ [@https://www.boost.org/doc/libs/release/doc/html/boost_asio.html Boost.ASIO]]
+[def __boost_asio__ [@https://www.boost.org/doc/libs/release/doc/html/boost_asio.html Boost.Asio]]
 [def __boost_move__ [@https://www.boost.org/doc/libs/release/doc/html/move.html Boost.Move]]
 [def __boost_locale__ [@https://www.boost.org/doc/libs/release/libs/locale/doc/html/index.html Boost.Locale]]
 [def __boost_type_index__ [@https://www.boost.org/doc/libs/release/doc/html/boost_typeindex.html Boost.TypeIndex]]