Fix high certainty warnings from PVS-studio (#5115)

* Fix high certainty warnings from PVS-studio

- Introduced FLATBUFFERS_ATTRIBUTE macro to use [[attribute]] if modern C++ compiler used

* Update the note about __cplusplus usage in the MSVC

include/flatbuffers/registry.h

@@ -72,7 +72,7 @@ class Registry {
       return DetachedBuffer();
     }
     // We have a valid FlatBuffer. Detach it from the builder and return.
-    return parser.builder_.ReleaseBufferPointer();
+    return parser.builder_.Release();
   }
 
   // Modify any parsing / output options used by the other functions.