Added _memmove_words

Added a memmove() variant for Dalvik's System.arraycopy()
implementation.  It guarantees 16-bit or 32-bit atomicity depending
on the alignment of the arguments.

Bug 3398352

(cherry-pick from master)

Change-Id: I5e64de1c76971ba234bf2dd05477ba390e0412a4
2 files changed