[PATCH, libstdc++] Fix missing gthr-default.h issue on libstdc++ configure

[Rainer Orth]

Pavel Chupin <pavel.v.chupin@gmail.com> writes:

> Could you try this fix?

Duplicating this much info from libgcc is certainly the wrong (read:
unmaintainable) approach.

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University