[C++] g++ isn't checking for class abstractness at instanciation time

[Martin v. Loewis]

> The following is a test case, adapted from a post on
> news:fr.comp.lang.c++ , demonstrating a bug in g++'s template
> instanciation machinery.  The call g<int>() is ill-formed and should
> be rejected.

Now that I started to clean up, I found that this is also fixed. Not
that you wouldn't know, anyway :-)

Regards,
Martin