frameworks/native: Add support for custom layers in Surfaceflinger.

  - Check for the EXT_ONLY layer and add only that layer to external
    list and do not add that layer to the primary list
  - Check for INT_ONLY layer and remove that layer from external list
  - These are added to support EXTERNAL_ONLY & INTERNAL_ONLY feature

Change-Id: I8f84eeacebf97d44446f319f69b8a73e56f2cb6d

Conflicts:

	services/surfaceflinger/Layer.cpp
	services/surfaceflinger/Layer.h
	services/surfaceflinger/SurfaceFlinger.cpp
(cherry picked from commit 42cd6bd3bc9e8d1e1eaabaaa06d16803b45942bd)
(cherry picked from commit 62af24e70035866aa8e8741a6f058fa8309d0028)
(cherry picked from commit 97112b478210c2adebdc1c0b41b60444e9ce6767)