Make fenv.h FE_* macros usable in #if (bug 3439)

[Markus Trippelsdorf]

On 2012.11.03 at 02:01 +0000, Joseph S. Myers wrote:
> This patch fixes the remaining part of bug 3439, FE_* constants in
> fenv.h not being usable in #if, in the same way as my recent fix for
> math.h constants (as suggested by Paul Eggert in that bug).

I now get:
...
make[2]: *** [/var/tmp/glibc-build/math/test-fenv.out] Error 1

math % cat test-fenv.out
Test: Initially all exceptions should be cleared
  Pass: Exception "DIVBYZERO" is not set
  Pass: Exception "INVALID" is not set
  Fail: Exception "INEXACT" is set
  Pass: Exception "UNDERFLOW" is not set
  Pass: Exception "OVERFLOW" is not set

-- 
Markus