PowerPC LE strchr

PowerPC LE strchr
http://sourceware.org/ml/libc-alpha/2013-08/msg00101.html

Adds little-endian support to optimised strchr assembly.  I've also
tweaked the big-endian code a little.  In power7/strchr.S there's a
check in the tail of the function that we didn't match 0 before
finding a c match, done by comparing leading zero counts.  It's just
as valid, and quicker, to compare the raw output from cmpb.

Another little tweak is to use rldimi/insrdi in place of rlwimi for
the power7 strchr functions.  Since rlwimi is cracked, it is a few
cycles slower.  rldimi can be used on the 32-bit power7 functions
too.

	* sysdeps/powerpc/powerpc64/power7/strchr.S (strchr): Add little-endian
	support.  Correct typos, formatting.  Optimize tail.  Use insrdi
	rather than rlwimi.
	* sysdeps/powerpc/powerpc32/power7/strchr.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/strchrnul.S (__strchrnul): Add
	little-endian support.  Correct typos.
	* sysdeps/powerpc/powerpc32/power7/strchrnul.S: Likewise.  Use insrdi
	rather than rlwimi.
	* sysdeps/powerpc/powerpc64/strchr.S (rTMP4, rTMP5): Define.  Use
	in loop and entry code to keep "and." results.
	(strchr): Add little-endian support.  Comment.  Move cntlzd
	earlier in tail.
	* sysdeps/powerpc/powerpc32/strchr.S: Likewise.