Revert "Change memcpy/memset/memmove to have dest and source alignments."

This reverts commit r253512.

This likely broke the bots in:
http://lab.llvm.org:8011/builders/clang-ppc64-elf-linux2/builds/20202
http://bb.pgr.jp/builders/clang-3stage-i686-linux/builds/3787

llvm-svn: 253542