libm: Check for NEON support when choosing fast pow()

Change-Id: If981f6d00325fd599e8fa975782adcd9016b5e55
libc: Add optimized memcpy for Cortex-A15

 * This version is from Newlib and is written/recommended by ARM as the best
   routine for Cortex-A15.

Change-Id: Ie9c2817dabda929ae4efaada5f6d467d53551ba4

Conflicts:

	libc/Android.mk