Deal with newer FFmpeg API.

Index: Core/HLE/sceMpeg.cpp
--- Core/HLE/sceMpeg.cpp.orig
+++ Core/HLE/sceMpeg.cpp
@@ -108,6 +108,7 @@ static bool useRingbufferPutCallbackMulti = true;
 #ifdef USE_FFMPEG 
 
 extern "C" {
+#include "libavcodec/avcodec.h"
 #include "libavformat/avformat.h"
 #include "libavutil/imgutils.h"
 #include "libswscale/swscale.h"
@@ -801,7 +802,7 @@ static bool InitPmp(MpegContext * ctx){
 	pmp_want_pix_fmt = AV_PIX_FMT_RGBA;
 
 	// Create H264 video codec
-	AVCodec * pmp_Codec = avcodec_find_decoder(AV_CODEC_ID_H264);
+	const AVCodec * pmp_Codec = avcodec_find_decoder(AV_CODEC_ID_H264);
 	if (pmp_Codec == NULL){
 		ERROR_LOG(ME, "Can not find H264 codec, please update ffmpeg");
 		return false;
