Make cpu-specific optimizations simpler, smarter, and more compatible with CM

infer what we use TARGET_ARCH_VARIANT_CPU for form TARGET_CPU_VARIANT
if TARGET_ARCH_VARIANT_CPU is undefined (as is the case with a virgin CM
device tree.
(based on 720710b - build: Cleanup CPU-specific optimizations (4 weeks ago) <Steve Kondik>)

assume some things are always true, and remove vestigial variables

Change-Id: I7e5c5809b1dc3f19e99cb153461876077b237345

Conflicts:
	core/combo/arch/arm/armv7-a-neon.mk
	core/combo/arch/arm/armv7-a.mk

Conflicts:
	core/combo/arch/arm/armv7-a-neon.mk
	core/combo/arch/arm/armv7-a.mk
Revert "Activated super saiyan! Jk lol. Add gcc 4.8"

This reverts commit deb25f6c66159a5aa0ed33fb76e9da2d678c604d.
Revert "Revert "Revert "Prepare upcoming GCC 4.8 release."""

This reverts commit 496126794d81997f42fde61305d7ad30667dcbc8.