add exynos4 enhancements

Conflicts:
	include/ui/GraphicBufferMapper.h

	modified:   include/ui/GraphicBuffer.h
	modified:   include/ui/GraphicBufferAllocator.h
	modified:   include/ui/GraphicBufferMapper.h
	modified:   libs/ui/GraphicBufferAllocator.cpp

Change-Id: I536893d008eb0ff15295971176c71557a54250fa