Suppress/fix some msvc and gcc compiler warnings ([57494]).

[SVN r60291]

base_from_member_test.cpp

@@ -281,7 +281,7 @@ object_id_compare::operator ()
         }
         else
         {
-            return a.second->before( *b.second );
+            return a.second->before( *b.second ) != 0;
         }
     }
 }