Taking function objects by value instead of as references-to-const. This does not work on MSVC6.5, so the BOOST_MSVC_ONLY macro was added to make them references-to-const for only that compiler.

- Borland C++ no longer requires hacks to make function pointers work
- On any compiler other than MSVC, free functions can be assigned to Boost.Function objects without the explicit '&'


[SVN r11943]

include/boost/function/function_base.hpp

@@ -25,6 +25,12 @@
 #include <boost/type_traits.hpp>
 #include <boost/ref.hpp>
 
+#ifdef BOOST_MSVC
+#  define BOOST_MSVC_ONLY(x) x
+#else
+#  define BOOST_MSVC_ONLY(x)
+#endif // not MSVC
+
 namespace boost {
   namespace detail {
     namespace function {