Edit PowerPC assembly for .and, .cms, .ior, .xor, .zer

Edit PowerPC assembly for .and, .cms, .ior, .xor, .zer

Remove one addi instruction from some loops.  These loops had
increased 2 pointers, they now increase 1 index.  I must initialize
the index, so I add "li r6, 0" before each loop.

Change .zer to use subf instead of neg, add.

Change .xor to take the size on the real stack, as .and and .or have
done since 81c677d.