h264: increase MAX_SLICES to 32

H264 streams from CounterPath Bria and some Cisco phones need an
increased pool for correct decoding.

Bug-Id: 645
Sample-Id: bria-h264.mka

libavcodec/h264.h

@@ -63,7 +63,7 @@
  * The maximum number of slices supported by the decoder.
  * must be a power of 2
  */
-#define MAX_SLICES 16
+#define MAX_SLICES 32
 
 #ifdef ALLOW_INTERLACE
 #define MB_MBAFF(h)    h->mb_mbaff