Added LdrbAnd2Ldrb Peephole optimizer for arm

Changes the following code:
  ldrb dst1, [REF]
  and  dst2, dst1, #255
  # dealloc dst1
to
  ldrb dst2, [REF]

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24672 3ad0048d-3df7-0310-abae-a5850022a9f2