libstagefright: Allow using camera recording buffer as input for encoder

Vastly improves camcorder framerate when recording 720p videos (from ~18fps to ~29,5fps)
Useful for SEMC 2011 devices, which don't have a powerful enough cpu
Can be enabled with global cflag SEMC_ICS_CAMERA_BLOB

Change-Id: I6dce1390bd611e9ce318d2aef0da22f843a2632b