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

Change-Id: Ie7bd246305ef0ff8290513663327c5b81680368d
diff --git a/libc/Android.mk b/libc/Android.mk
index d940753..647739e 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -269,6 +269,7 @@
 	bionic/libc_init_common.c \
 	bionic/logd_write.c \
 	bionic/md5.c \
+	bionic/memmove_words.c \
 	bionic/pututline.c \
 	bionic/realpath.c \
 	bionic/sched_getaffinity.c \