When fixing namespace issues for <fenv.h> functions I missed one call
to fesetenv for powerpc-nofpu. This patch changes this to a call to
__fesetenv.
Tested for powerpc-nofpu; it fixes the previously observed math.h
linknamespace test failures.
[BZ #17748]
* sysdeps/powerpc/nofpu/feholdexcpt.c (__feholdexcept): Call
__fesetenv instead of fesetenv.