refactor HWComposer to break dependency with the HAL headers

HWComposer must abstract the HWC HAL entirely, so that the
HAL can continue to evolve (and break binary compatibility)
without breaking SurfaceFlinger. The HWC data structure had
leaked outside of HWComposer, this is now fixed.

We now have an abstract interface that provide all the
needed functionality, HWCompose provides concrete
implementations of it based on the the HWC version.

Change-Id: I40c4676dc986b682ede5520a1c60efe64037b0bb
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 393599f..7a164aa 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -64,8 +64,8 @@
     bool isFixedSize() const;
 
     // LayerBase interface
-    virtual void setGeometry(hwc_layer_t* hwcl);
-    virtual void setPerFrameData(hwc_layer_t* hwcl);
+    virtual void setGeometry(HWComposer::HWCLayerInterface& layer);
+    virtual void setPerFrameData(HWComposer::HWCLayerInterface& layer);
     virtual void onDraw(const Region& clip) const;
     virtual uint32_t doTransaction(uint32_t transactionFlags);
     virtual void lockPageFlip(bool& recomputeVisibleRegions);