af_pan cannot parse arguments from example in documentation

[sghpunk]

Summary of the bug:
ffmpeg gives an error: 'Expected out channel name, got " FL < FL"'
How to reproduce:

% ffmpeg -i file.mpg -f wav -map 0:a:1 -filter:a [in]pan="stereo: FL < FL + 0.7*FC + 0.6*LFE + 0.7*BL + 0.7*SL : FR < FR + 0.7*FC + 0.6*LFE + 0.7*BR + 0.7*SR"[out] file.wav

ffmpeg version 1.2 Copyright (c) 2000-2013 the FFmpeg developers
  built on Apr 12 2013 09:56:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --prefix=/opt/ffmpeg-1.2 --disable-static --enable-shared --enable-gpl --enable-version3 --enable-doc --enable-postproc --disable-network --enable-memalign-hack --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libmp3lame --enable-libspeex --enable-libvorbis --enable-libx264 --enable-pthreads --enable-frei0r --cpu=amdfam10 --arch=amd64 --disable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --enable-libfreetype --enable-vaapi --enable-libopenjpeg --enable-x11grab --enable-libmp3lame --enable-librtmp --enable-libx264 --enable-libdc1394 --enable-libxvid --enable-avresample --extra-cflags='-g0 -s' --extra-cxxflags='-g0 -s' --build-suffix=-1.2 --extra-ldflags='-L/opt/ffmpeg-1.2/lib -Wl,-rpath,/opt/ffmpeg-1.2/lib'
  libavutil      52. 18.100 / 52. 18.100
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.104 / 54. 63.104
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 42.103 /  3. 42.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100

I found a regression and have patch submitted to ffmpeg-devel mailing list

[Michael Niedermayer]

patch applied