bionic: update memmove for 32 bits atomic

When src/dst are 32bits aligned, the updated memmove will guarantee
32bits atomic.

Change-Id: I21cb77451270d061b32e3e2d2fda22e7e373b7ff
Fix build for x86. Remove duplicate mcmchr from Android.mk. Other implemented in arch-x86/x86.mk

Change-Id: I90a562960b214dd02b015d3e2715f711907ae9e8