libstagefright: conditionally expose support for QCOM HW AAC decoder

Change-Id: Ifcbd89ef5cf84c18e53fc16abc53b9b807f73eb2
[3/3] av: Allow custom DOMX source instead of Google DOMX default

Part 3 of 3 patches: To allow omap4 devices to use custom "domx" source
via a new BoardConfig.mk item:
TI_CUSTOM_DOMX_PATH := device/<manufacturer>/<device-name>/domx

This setting provides for 3 changes during the build:
1. In hardware/ti/omap4xxx this settings stops standard Google domx
source from being built and changes the domx reference for tiutils.
2. In frameworks/base it changes the default openmax references for
frameworks/base/media/jni/mediaeditor/Android.mk to the new location
3. In frameworks/av changes the openmax references in 5 places, and adds
new includes in ACodec.cpp, CameraSource.cpp and OMXCodec.cpp

This commit is based on cherry-pick from omapzoom (with a more descriptive
BoardConfig setting name):
http://www.omapzoom.org/?p=platform/frameworks/base.git;a=commit;h=f7f929ff477955333bf7e7413a81a66d68

Change-Id: I67dee7e077cd850acad6a0d4afb70218a8b9f2cd