avcodec/diracdec: Change frame_number to 64bit as its a 32bit from the bitstream and we also have a -1 special case

Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
Fixes: 9291/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DIRAC_fuzzer-6324345860259840

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 462d1be6de)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/diracdec.c

@@ -129,7 +129,7 @@ typedef struct DiracContext {
     GetBitContext gb;
     AVDiracSeqHeader seq;
     int seen_sequence_header;
-    int frame_number;           /* number of the next frame to display       */
+    int64_t frame_number;       /* number of the next frame to display       */
     Plane plane[3];
     int chroma_x_shift;
     int chroma_y_shift;
@@ -2214,7 +2214,7 @@ static int dirac_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
     }
 
     if (*got_frame)
-        s->frame_number = picture->display_picture_number + 1;
+        s->frame_number = picture->display_picture_number + 1LL;
 
     return buf_idx;
 }