add "S263" fourcc

[ami_stuff]

this is "Lead H263 codec" with "Output Sorenson Video (Flash)" option enabled

​http://www.leadtools.com/help/leadtools/v15/multimedia/filters/filters/leadh263encoder%282.0%29_ui.htm

C:\>ffmpeg -i lead_h263_osv.avi
ffmpeg version N-36890-g67f5650 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jan 16 2012 21:57:13 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-ru
ntime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libope
ncore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --en
able-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger -
-enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwben
c --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-
libxvid --enable-zlib
  libavutil      51. 34.100 / 51. 34.100
  libavcodec     53. 56.105 / 53. 56.105
  libavformat    53. 30.100 / 53. 30.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 59.100 /  2. 59.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    51.  2.100 / 51.  2.100
[avi @ 020F2320] non-interleaved AVI
[avi @ 020F2320] max_analyze_duration 5000000 reached at 5040000
[avi @ 020F2320] Could not find codec parameters (Video: none (S263 / 0x33363253
), 192x128)
lead_h263_osv.avi: could not find codec parameters

[Michael Niedermayer]

patch applied