Bug 16198 is x86_64 fegetenv wrongly masking exceptions for which
traps are enabled, because that's a side-effect of the fnstenv
instruction. This patch fixes it to use fldenv immediately after
fnstenv, like the i386 version. Tested x86_64 and x86.
[BZ #16198]
* sysdeps/x86_64/fpu/fegetenv.c (fegetenv): Use fldenv after
fnstenv.
* math/test-fenv-preserve.c: New file.
* math/Makefile (tests): Add test-fenv-preserve.