mpegvideo: increase MAX_PICTURE_NUMBER.

avoid abort().

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo.h

@@ -60,7 +60,7 @@ enum OutputFormat {
 
 #define MAX_THREADS 32
 
-#define MAX_PICTURE_COUNT 32
+#define MAX_PICTURE_COUNT 34
 
 #define ME_MAP_SIZE 64
 #define ME_MAP_SHIFT 3