hwcomposer: Add HWC_BLIT compositiontype value

- HWC_BLIT this layer will be handled in the HWC, using a blit engine
- setting this will inform Surfaceflinger to flip FB_TARGET

Change-Id: I25d19ec41b57863d451c3e390109c912faf1381c
libhardware: Modify ifdefs for legacy DirectTrack

Change-Id: Id3a8adc3bd3b8fe5973e359b5268671f6fd26cd4

Conflicts:
	include/hardware/audio.h