Avoid localplt issues from x86 fereaiseexcept inline.

Building for x86_64 with float128 support, I get a localplt test
failure from lrintf128 calling feraiseexcept.

The problem is that an inline optimized version of feraiseexcept calls
__feraiseexcept_renamed in cases where it doesn't completely expand
inline, and that in turn is redirected to feraiseexcept for a library
call, so meaning the redirection of feraiseexcept to
__GI_feraiseexcept inside libm is lost for that call.

This patch fixes the problem by moving the redirect to an internal
header in the _LIBC case, with the internal header using
__GI_feraiseexcept where appropriate.

Tested for x86_64 (in conjunction with float128 patches).

	* sysdeps/x86/fpu/bits/fenv.h [_LIBC] (__feraiseexcept_renamed):
	Do not declare.
	* sysdeps/x86/fpu/include/bits/fenv.h [_LIBC &&
	__USE_EXTERN_INLINES] (__feraiseexcept_renamed): Declare here,
	redirected to __GI_feraiseexcept if [SHARED && IS_IN (libm)].