[3/3] libstagefright/videoeditor: 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 is a combination of cherry-picks from omapzoom (with a more descriptive
BoardConfig setting name):
http://www.omapzoom.org/?p=platform/frameworks/av.git;a=commit;h=8044105ca117c2e99b35ad9f341d630fc5a9d2e0
http://www.omapzoom.org/?p=platform/frameworks/av.git;a=commit;h=4adf712d1f3f2050fe0010652bbba7ecb8468870
http://www.omapzoom.org/?p=platform/frameworks/av.git;a=commit;h=fa37231ca59872ac491461ca3c14e019834848e5

Change-Id: Ia34ab95b230998f03a8078f046b62aa3298fce80