Allow a device to generically define its own headers

We have a few cases of devices including specific versions of projects
just because of modified headers (msm_mdp.h comes to mind), and I just
had enough of ifdeffing header files for specific cases (the P990 needs
a lot of these).
Now... if a target defines a TARGET_SPECIFIC_HEADER_PATH, any headers in
there will take precedence over the standard ones; for example, on the
p990, I have

TARGET_SPECIFIC_HEADER_PATH := device/lge/p990/include

which makes, for example, the
device/lge/p990/include/hardware_legacy/AudioHardwareInterface.h be
used instead of
hardware/libhardware_legacy/include/hardware_legacy/AudioHardwareInterface.h
whenever a source file uses <hardware_legacy/AudioHardwareInterface.h>

Change-Id: I41b62668b60e3f62a6ebd3738d8d2675103a81e6a
build: Enable Bionic optimizations on Cortex platforms

 * Enable the new NEON optimizations in Bionic when
   TARGET_ARCH_VARIANT_CPU is set.
 * NEON memcpy() optimization is disabled on A15 due to a regression.

Change-Id: I4862695812a70b75bdabc4398cb592157f3913c6

Conflicts:
	core/combo/arch/arm/armv7-a.mk
build: move bionic optimizations to NEON makefile

Change-Id: Idd495ddbb49f67fef5496456803263f8a23643c5

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

Conflicts:

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