Added a BOOST_DEPRECATED macro for deprecated symbol markup.

BOOST_DEPRECATED can be used to mark functions, types and objects as
deprecated, with a message with a recommendation of replacement. Using
such marked symbols in code will generate compiler warnings, with the
specified message, if possible.

The warnings can be suppressed if BOOST_ALLOW_DEPRECATED_SYMBOLS is defined.
Additionally, added support BOOST_ALLOW_DEPRECATED macro that not only
allows for deprecated symbols but also deprecated headers (i.e. defining
BOOST_ALLOW_DEPRECATED is equivalent to defining both
BOOST_ALLOW_DEPRECATED_SYMBOLS and BOOST_ALLOW_DEPRECATED_HEADERS).

include/boost/config/compiler/visualc.hpp

@@ -107,6 +107,14 @@
 #  define BOOST_NO_RTTI
 #endif
 
+// Deprecated symbol markup
+#if (_MSC_VER >= 1400)
+#define BOOST_DEPRECATED(msg) __declspec(deprecated(msg))
+#else
+// MSVC 7.1 only supports the attribute without a message
+#define BOOST_DEPRECATED(msg) __declspec(deprecated)
+#endif
+
 //
 // TR1 features:
 //