BufferQueue: Increase max slots from 32 to 64

Increases NUM_BUFFER_SLOTS from 32 to 64 and changes the mask
returned by IGBC::getReleasedBuffers from 32 to 64 bits.

Bug: 13174352
Change-Id: Ie8ef0853916cfb91f83881c7241886bb1950f01a
diff --git a/include/gui/BufferQueueDefs.h b/include/gui/BufferQueueDefs.h
index bccc881..83e9580 100644
--- a/include/gui/BufferQueueDefs.h
+++ b/include/gui/BufferQueueDefs.h
@@ -26,7 +26,7 @@
         // BufferQueue will keep track of at most this value of buffers.
         // Attempts at runtime to increase the number of buffers past this
         // will fail.
-        enum { NUM_BUFFER_SLOTS = 32 };
+        enum { NUM_BUFFER_SLOTS = 64 };
 
         typedef BufferSlot SlotsType[NUM_BUFFER_SLOTS];
     } // namespace BufferQueueDefs