When I run
```
php maintenance/runJobs.php --type webVideoTranscode
```
the outout say `Unrecognized option 'max_muxing_queue_size'`. 3a319b0ed864 introduced this option, but my server using ffmpeg 2.8.15.
I think we should ensure backward compatibility and selectively add `max_muxing_queue_size` option.
Complete output:
```
[razesoldier@wiki w]$ php maintenance/runJobs.php --type webVideoTranscode2019-02-17 07:10:53 webVideoTranscode File:How_a_Makarov_pistol_works.mp4 transcodeMode=derivative transcodeKey=1080p.webm prioritized= requestId=48219542f36290cb728ad6a6 (id=15439,timestamp=20190217071044) STARTING
2019-02-17 07:10:55 webVideoTranscode File:How_a_Makarov_pistol_works.mp4 transcodeMode=derivative transcodeKey=1080p.webm prioritized= requestId=48219542f36290cb728ad6a6 (id=15439,timestamp=20190217071044) t=1950 error='/usr/bin/ffmpeg' -y -i '/srv/gunwiki/w/images/c/cf/How_a_Makarov_pistol_works.mp4' -threads 1 -pix_fmt yuv420p -crf '10' -qmin '1' -qmax '51' -vb '4096000' -vcodec libvpx -slices '4' -g '240' -speed 4 -f webm -s 1920x1080 -max_muxing_queue_size 1024 -an -pass '1' -passlogfile '/tmp/transcode_1080p.webmea8103dd94ce.webm.log' /dev/null
Exitcode: 1
Memory: 2097152
ffmpeg version 2.8.15 Copyright (c) 2000-2018 the FFmpeg developers
built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-28)
configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --extra-ldflags='-Wl,-z,relro ' --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-amrwbenc --enable-version3 --enable-bzlib --disable-crystalhd --enable-gnutls --enable-ladspa --enable-libass --enable-libcdio --enable-libdc1394 --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libx264 --enable-libx265 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
libavutil 54. 31.100 / 54. 31.100
libavcodec 56. 60.100 / 56. 60.100
libavformat 56. 40.101 / 56. 40.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 40.101 / 5. 40.101
libavresample 2. 1. 0 / 2. 1. 0
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.101 / 1. 2.101
libpostproc 53. 3.100 / 53. 3.100
Unrecognized option 'max_muxing_queue_size'.
Error splitting the argument list: Option not found
```