The fallback implementation of fesetexceptflag currently fails if any
exceptions are specified. It should always succeed, because the
exception state is always that all exceptions (if any are defined in
<fenv.h> but not supported in this configuration) are always clear,
just as fallback fetestexcept always succeeds and fallback fesetenv
always succeeds unless asked to set FE_NOMASK_ENV.
This patch fixes it accordingly. Together with the patch to
test-fexcept.c to allow feraiseexcept to fail in another place, this
stops that test from failing for MIPS soft-float.
Tested for mips64 soft-float.
[BZ #21028]
* math/fsetexcptflg.c (__fesetexceptflag): Always return 0.
* math/test-fexcept.c (test_set): Allow failure of feraiseexcept
if EXCEPTION_TESTS returns false.
