Windows: Mandatory notification extension (pull request 72)
Device sync: Sanitized playlist filename (bug 1788)
Device sync: Sanitize mount point encoding (bug 1785)
Extensions: Merge audio/video converter extensions (bug 1783)

There were similar extensions which have been folded into one:

 - 2 similar audio extensions -> the audio_converter extension
 - 2 similar video extensions -> the video_converter extension

With this change it's now possible to change the video output format in
the advanced settings to mp4 (default) or avi.
Merge branch 'master' of git://github.com/gpodder/gpodder