[v3] cleanup testsuite for newlib targets

[Benjamin Kosnik]

> #ifdef __GXX_EXPERIMENTAL_CXX0X__
> #include <cfenv>
> #else
> #include_next <fenv.h>
> #endif

Yes.

It looks like this will meet TR1 1.3p3.

Please do it consistently for new c_compatibilty includes for C++0x.

best,
benjamin