This change exposes a few bugs in the soft-fp implementations for PPC.
The current feholdexcept implementation has where it uses fesetenv to
resort the current env:

/* Get the current state. */
fegetenv (envp);

u.fenv = *envp;
/* Clear everything except the rounding mode. */
u.l[0] &= 0x3;

/* ?? Should we clear the disabled exceptions as well ?? */

/* Put the new state in effect. */
fesetenv (envp);

Which is incorrect. It should disable exceptions and pass the updated
env to fesetenv:

/* Disable exceptions */
u.l[1] = FE_ALL_EXCEPT;

/* Put the new state in effect. */
fesetenv (&u.fenv);

Finally the powerpc/nofpu version is missing the libm_hidden_def which
results in a link error in make check.

The attached patch fixes all of these problems.