ffmpeg: Fix memory corruption with ffserver

Bug has been introduced by:
commit 1cede1d011
Author: Anton Khirnov <anton@khirnov.net>
Date:   Sat Jun 25 07:43:49 2011 +0200

    ffmpeg: factor common code from new_a/v/s/d_stream to new_output_stream()

ffmpeg.c

@@ -3636,15 +3636,18 @@ static int read_ffserver_streams(OptionsContext *o, AVFormatContext *s, const ch
         AVStream *st;
         OutputStream *ost;
         AVCodec *codec;
+        AVCodecContext *avctx;
 
         codec = avcodec_find_encoder(ic->streams[i]->codec->codec_id);
         ost   = new_output_stream(o, s, codec->type);
         st    = ost->st;
+        avctx = st->codec;
 
         // FIXME: a more elegant solution is needed
         memcpy(st, ic->streams[i], sizeof(AVStream));
         st->info = av_malloc(sizeof(*st->info));
         memcpy(st->info, ic->streams[i]->info, sizeof(*st->info));
+        st->codec= avctx;
         avcodec_copy_context(st->codec, ic->streams[i]->codec);
 
         if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO && !ost->stream_copy)