Added BOOST_MAY_ALIAS and BOOST_NO_MAY_ALIAS macros.

The macros can be used to mark types that can alias other types (i.e. break
C++ strict aliasing rules).

test/config_info.cpp

@@ -1152,6 +1152,8 @@ void print_boost_macros()
    PRINT_MACRO(BOOST_FORCEINLINE);
    PRINT_MACRO(BOOST_NOINLINE);
    PRINT_MACRO(BOOST_FALLTHROUGH);
+   PRINT_MACRO(BOOST_MAY_ALIAS);
+   PRINT_MACRO(BOOST_NO_MAY_ALIAS);
 }
 
 void print_separator()