PowerPC LE strcmp and strncmp

PowerPC LE strcmp and strncmp
http://sourceware.org/ml/libc-alpha/2013-08/msg00099.html

More little-endian support.  I leave the main strcmp loops unchanged,
(well, except for renumbering rTMP to something other than r0 since
it's needed in an addi insn) and modify the tail for little-endian.

I noticed some of the big-endian tail code was a little untidy so have
cleaned that up too.

	* sysdeps/powerpc/powerpc64/strcmp.S (rTMP2): Define as r0.
	(rTMP): Define as r11.
	(strcmp): Add little-endian support.  Optimise tail.
	* sysdeps/powerpc/powerpc32/strcmp.S: Similarly.
	* sysdeps/powerpc/powerpc64/strncmp.S: Likewise.
	* sysdeps/powerpc/powerpc32/strncmp.S: Likewise.
	* sysdeps/powerpc/powerpc64/power4/strncmp.S: Likewise.
	* sysdeps/powerpc/powerpc32/power4/strncmp.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/strncmp.S: Likewise.
	* sysdeps/powerpc/powerpc32/power7/strncmp.S: Likewise.