[v3] use_facet<ctype> clean up

[Luis Machado]

> I got the exact same thing initially as well (
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37478 ) and to solve it I
> had to basically to a clean bootstrap (like rm -rf gcc-build/*
> re-config etc.). The build system does ok with detecting changes to
> source and header files but exports and other things, not so much.
> 
> Cheers,
> Chris

Oh great. So it's not really a regression after all. Thanks for the
hint. :-)

Thanks,
Luis