merged compatibility patch from RC_0_16

include/libtorrent/config.hpp

@@ -67,6 +67,20 @@ POSSIBILITY OF SUCH DAMAGE.
 #endif
 #endif
 
+// backwards compatibility with older versions of boost
+#if !defined BOOST_SYMBOL_EXPORT && !defined BOOST_SYMBOL_IMPORT
+# ifdef _MSC_VER
+#  define BOOST_SYMBOL_EXPORT __declspec(dllexport)
+#  define BOOST_SYMBOL_IMPORT __declspec(dllimport)
+# elif __GNU__ >= 4
+#  define BOOST_SYMBOL_EXPORT __attribute__((visibility("default")))
+#  define BOOST_SYMBOL_IMPORT __attribute__((visibility("default")))
+# else
+#  define BOOST_SYMBOL_EXPORT
+#  define BOOST_SYMBOL_IMPORT
+# endif
+#endif
+
 #if defined TORRENT_BUILDING_SHARED
 # define TORRENT_EXPORT BOOST_SYMBOL_EXPORT
 #elif defined TORRENT_LINKING_SHARED

src/asio.cpp

@@ -1,3 +1,7 @@
 // builds all boost.asio source as a separate compilation unit
-#include <boost/asio/impl/src.hpp>
+#include <boost/version.hpp>
+
+#if BOOST_VERSION >= 104610
+#include <boost/asio/impl/src.hpp>
+#endif