FFmpeg Stack Buffer Overflow in MPEG-PS Muxer via mpegenc.c

FFmpeg before commit 9d786e4 contains a stack buffer overflow in the MPEG-PS muxer (libavformat/mpegenc.c). When muxing input with more streams than the muxer's fixed-size stack buffer accommodates, the buffer is overflowed. A crafted input with an excessive number of streams triggers the overflow during MPEG-PS muxing.