"playlistdelete" takes a song position, not a song id.  There are
no song ids in stored playlists.

Over the years, a lot of commands have been added to MPD which were
documented only in the wiki
(http://mpd.wikia.com/wiki/Protocol_Reference).  Merge all missing
commands from there.

Correct lots of grammar and spelling errors.  Unify some phrases.

Wrapped keywords in DocBook tags where appropriate.

The attribute value must be lower case: <arg rep="repeat">

The goal is to have one structured document which is the authoritative
protocol specification.  The documentation which currently resides in
the wiki will be merged.