PowerPC LE memset

PowerPC LE memset
http://sourceware.org/ml/libc-alpha/2013-08/msg00104.html

One of the things I noticed when looking at power7 timing is that rlwimi
is cracked and the two resulting insns have a register dependency.
That makes it a little slower than the equivalent rldimi.

	* sysdeps/powerpc/powerpc64/memset.S: Replace rlwimi with
        insrdi.  Formatting.
	* sysdeps/powerpc/powerpc64/power4/memset.S: Likewise.
	* sysdeps/powerpc/powerpc64/power6/memset.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/memset.S: Likewise.
	* sysdeps/powerpc/powerpc32/power4/memset.S: Likewise.
	* sysdeps/powerpc/powerpc32/power6/memset.S: Likewise.
	* sysdeps/powerpc/powerpc32/power7/memset.S: Likewise.