#6 add sort playlist command

[rvp_nl]

It would be nice to have a "playlist sort" command such
that the playlist is sorted alphabetically (usefull if
mp3 albums are stored in folders: mod_playlist_load
does not sort filenams) . The mod_keyseq relies on a
sorted playlist. I have implemented a sorting routine
(using quicksort) that sorts the playlist. Key method
to sort a linked list is to temporarily create an array
that represents the linked list and use that to sort
the list.
I have a patch ready that adds sorting to mod_playlist.