mpegvideo: double thread limit

16 seems a bit tight for current high end and expected near term future boxes.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo.h

@@ -58,7 +58,7 @@ enum OutputFormat {
 #define MAX_FCODE 7
 #define MAX_MV 2048
 
-#define MAX_THREADS 16
+#define MAX_THREADS 32
 
 #define MAX_PICTURE_COUNT 32