avcodec/vqcdec: Check width & 15

Various parts of the code assume that width can be divided by various powers of 2
without rounding

Fixes: out of array access
Fixes: 53623/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VQC_fuzzer-6209269924233216

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/vqcdec.c

@@ -71,6 +71,9 @@ static av_cold int vqc_decode_init(AVCodecContext * avctx)
     static AVOnce init_static_once = AV_ONCE_INIT;
     VqcContext *s = avctx->priv_data;
 
+    if (avctx->width & 15)
+        return AVERROR_PATCHWELCOME;
+
     s->vectors = av_malloc((avctx->width * avctx->height * 3) / 2);
     if (!s->vectors)
         return AVERROR(ENOMEM);