Fix powerpc64 ceil, rint etc. on sNaN input (bug 20160).

The powerpc64 versions of ceil, floor, round, trunc, rint, nearbyint
and their float versions return sNaN for sNaN input when they should
return qNaN.  This patch fixes them to add a NaN argument to itself to
quiet sNaNs before returning.

Tested for powerpc64.

	[BZ #20160]
	* sysdeps/powerpc/powerpc64/fpu/s_ceil.S (__ceil): Add NaN
	argument to itself before returning the result.
	* sysdeps/powerpc/powerpc64/fpu/s_ceilf.S (__ceilf): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_floor.S (__floor): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_floorf.S (__floorf): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_nearbyint.S (__nearbyint):
	Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_nearbyintf.S (__nearbyintf):
	Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_rint.S (__rint): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_rintf.S (__rintf): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_round.S (__round): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_roundf.S (__roundf): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_trunc.S (__trunc): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_truncf.S (__truncf): Likewise.