Fix libm feupdateenv namespace (bug 17748).

Fix libm feupdateenv namespace (bug 17748).

Concluding the fixes for C90 libm functions calling C99 fe* functions,
this patch fixes the case of feupdateenv by making it a weak alias for
__feupdateenv and making the affected code call __feupdateenv.

Tested for x86_64 (testsuite, and that installed stripped shared
libraries are unchanged by the patch).  Also tested for ARM
(soft-float) that the math.h linknamespace tests now pass.

	[BZ #17748]
	* include/fenv.h (__feupdateenv): Use libm_hidden_proto.
	* math/feupdateenv.c (__feupdateenv): Use libm_hidden_def.
	* sysdeps/aarch64/fpu/feupdateenv.c (feupdateenv): Rename to
	__feupdateenv and define as weak alias of __feupdateenv.  Use
	libm_hidden_weak.
	* sysdeps/alpha/fpu/feupdateenv.c (__feupdateenv): Use
	libm_hidden_def.
	* sysdeps/arm/feupdateenv.c (feupdateenv): Rename to __feupdateenv
	and define as weak alias of __feupdateenv.  Use libm_hidden_weak.
	* sysdeps/hppa/fpu/feupdateenv.c (feupdateenv): Likewise.
	* sysdeps/i386/fpu/feupdateenv.c (__feupdateenv): Use
	libm_hidden_def.
	* sysdeps/ia64/fpu/feupdateenv.c (feupdateenv): Rename to
	__feupdateenv and define as weak alias of __feupdateenv.  Use
	libm_hidden_weak.
	* sysdeps/m68k/fpu/feupdateenv.c (__feupdateenv): Use
	libm_hidden_def.
	* sysdeps/mips/fpu/feupdateenv.c (feupdateenv): Rename to
	__feupdateenv and define as weak alias of __feupdateenv.  Use
	libm_hidden_weak.
	* sysdeps/powerpc/fpu/feupdateenv.c (__feupdateenv): Use
	libm_hidden_def.
	* sysdeps/powerpc/nofpu/feupdateenv.c (__feupdateenv): Likewise.
	* sysdeps/powerpc/powerpc32/e500/nofpu/feupdateenv.c
	(__feupdateenv): Likewise.
	* sysdeps/s390/fpu/feupdateenv.c (feupdateenv): Rename to
	__feupdateenv and define as weak alias of __feupdateenv.  Use
	libm_hidden_weak.
	* sysdeps/sh/sh4/fpu/feupdateenv.c (feupdateenv): Likewise.
	* sysdeps/sparc/fpu/feupdateenv.c (__feupdateenv): Use
	libm_hidden_def.
	* sysdeps/tile/math_private.h (__feupdateenv): New inline
	function.
	* sysdeps/x86_64/fpu/feupdateenv.c (__feupdateenv): Use
	libm_hidden_def.
	* sysdeps/generic/math_private.h (default_libc_feupdateenv): Call
	__feupdateenv instead of feupdateenv.
	(default_libc_feupdateenv_test): Likewise.
	(libc_feresetround_ctx): Likewise.