avcodec/vc2enc: Fix overflows with storing large values

Fixes: left shift of 1431634944 by 2 places cannot be represented in type 'int'
Fixes: left shift of 1073741824 by 1 places cannot be represented in type 'int'
Fixes: 69061/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC2_fuzzer-6325700826038272

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 af99358353)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/vc2enc.c

@@ -185,7 +185,9 @@ typedef struct VC2EncContext {
 static av_always_inline void put_vc2_ue_uint(PutBitContext *pb, uint32_t val)
 {
     int i;
-    int pbits = 0, bits = 0, topbit = 1, maxval = 1;
+    int bits = 0;
+    unsigned topbit = 1, maxval = 1;
+    uint64_t pbits = 0;
 
     if (!val++) {
         put_bits(pb, 1, 1);
@@ -202,12 +204,13 @@ static av_always_inline void put_vc2_ue_uint(PutBitContext *pb, uint32_t val)
 
     for (i = 0; i < bits; i++) {
         topbit >>= 1;
+        av_assert2(pbits <= UINT64_MAX>>3);
         pbits <<= 2;
         if (val & topbit)
             pbits |= 0x1;
     }
 
-    put_bits(pb, bits*2 + 1, (pbits << 1) | 1);
+    put_bits64(pb, bits*2 + 1, (pbits << 1) | 1);
 }
 
 static av_always_inline int count_vc2_ue_uint(uint32_t val)