Add a RenderBuffer object to store stencil buffers.
Bug #7146141

This change is needed to add a render buffer cache to avoid
creating and destroying stencil buffers on every frame.

This change also allows the renderer to use a 1 bit or 4 bit
stencil buffer whenever possible.

Finally this change fixes a bug introduced by a previous CL
which causes the stencil buffer to not be updated in certain
conditions. The fix relies on a new optional parameter in
drawColorRects() that can be used to avoid performing a
quickReject on rectangles generated by the clip region.

Change-Id: I2f55a8e807009887b276a83cde9f53fd5c01199f
diff --git a/libs/hwui/Debug.h b/libs/hwui/Debug.h
index dfc4e25..5f8baac 100644
--- a/libs/hwui/Debug.h
+++ b/libs/hwui/Debug.h
@@ -44,6 +44,9 @@
 // Turn on to display info about layers
 #define DEBUG_LAYERS 0
 
+// Turn on to make stencil operations easier to debug
+#define DEBUG_STENCIL 0
+
 // Turn on to display debug info about 9patch objects
 #define DEBUG_PATCHES 0
 // Turn on to "explode" 9patch objects