Fixed off by one packet size allocation in the smacker demuxer.

Signed-off-by: Martin Storsjö <martin@martin.st>
(cherry picked from commit a92d0fa5d2)

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/smacker.c

@@ -294,7 +294,7 @@ static int smacker_read_packet(AVFormatContext *s, AVPacket *pkt)
         }
         if (frame_size < 0)
             return AVERROR_INVALIDDATA;
-        if (av_new_packet(pkt, frame_size + 768))
+        if (av_new_packet(pkt, frame_size + 769))
             return AVERROR(ENOMEM);
         if(smk->frm_size[smk->cur_frame] & 1)
             palchange |= 2;