Add a patch which fixes an obviously bogus preprocessor conditional;
in our case, __STDC_VERSION__ isn't defined when built as C++.
The fix isn't completeely right, it insists on <fenv.h> if built as C++.
Not entirely unreasonable, and makes this build on NetBSD/powerpc as well,
which doesn't like the redefinition of fegetround() and fesetround().
Bump PKGREVISION.

(he)