[Bug c++/13981] Give message about incomplete class that might be implicitly upcasted.

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13981

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Patchlet posted here:

  http://gcc.gnu.org/ml/gcc-patches/2013-08/msg01588.html