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/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
index 09e5544..3f0c854 100644
--- a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
+++ b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
@@ -152,10 +152,10 @@
     // Since we present a single producer interface to the GLES driver, but
     // are internally muxing between the sink and scratch producers, we have
     // to keep track of which source last returned each producer slot from
-    // dequeueBuffer. Each bit in mLastSlotSource corresponds to a producer
+    // dequeueBuffer. Each bit in mProducerSlotSource corresponds to a producer
     // slot. Both mProducerSlotSource and mProducerBuffers are indexed by a
     // "producer slot"; see the mapSlot*() functions.
-    uint32_t mProducerSlotSource;
+    uint64_t mProducerSlotSource;
     sp<GraphicBuffer> mProducerBuffers[BufferQueue::NUM_BUFFER_SLOTS];
 
     // The QueueBufferOutput with the latest info from the sink, and with the