build: move bionic optimizations to NEON makefile

Change-Id: Idd495ddbb49f67fef5496456803263f8a23643c5
build: Relax Cortex CFLAGS

 * Always set march=armv7-a
 * Use mtune instead of mcpu. Bad code is generated on A15 otherwise.

Change-Id: Idf8ced8eb0e9d3d4676ca8ec69bf56aed5533bf4
Merge commit 'refs/changes/12/32012/1' of http://review.cyanogenmod.org/CyanogenMod/android_build into cm-10.1
Merge commit 'refs/changes/18/32018/2' of http://review.cyanogenmod.org/CyanogenMod/android_build into cm-10.1