surfaceflinger: add surface abstraction to RE

Add Surface to RenderEngine.  Unlike Texture or Mesh,

 - Surface assumes EGL
 - Surface manages an EGLSurface
 - Surface is in android::RE namespace

Test: builds
Change-Id: Id0ac0f5c19fc144ec7dd44c045fa920b97527362
diff --git a/services/surfaceflinger/Android.mk b/services/surfaceflinger/Android.mk
index ecee8ce..deead06 100644
--- a/services/surfaceflinger/Android.mk
+++ b/services/surfaceflinger/Android.mk
@@ -41,6 +41,7 @@
     RenderEngine/ProgramCache.cpp \
     RenderEngine/GLExtensions.cpp \
     RenderEngine/RenderEngine.cpp \
+    RenderEngine/Surface.cpp \
     RenderEngine/Texture.cpp \
     RenderEngine/GLES20RenderEngine.cpp \
     LayerProtoHelper.cpp \