playlist (which is currently easily the #1 requested feature).  Although
there's still issues to be solved with it, it seems to work pretty well at this
point, I've been running this code for a few days now.

How it works so far:

* You must enable it by selecting "Show Upcoming Playlist" from the View menu.
* When the upcoming playlist is enabled, it takes over control of playback
  completely.  You can drag-and-drop tracks onto the playlist to add them to
  the end of the line, or you can use the context menu's Add to end of upcoming
  playlist entry.
* If loop playback is disabled, then entries will be added to the end of the
  playlist as entries disappear.
* Hitting Next (or double-clicking an item while a track is playing) will cause
  the currently playing track to disappear.  The History playlist doesn't play
  too well with the upcoming playlist yet, so if you want to keep the songs you
  played, you're better off making a normal playlist.
* On that note, double-clicking a song will add it to the beginning of the
  queue and immediately start playing it.
* Random play should work as normal.  If it doesn't, it's a bug.
* When the list becomes empty, playback stops.
* There is also a selection in the Settings menu, "Save Upcoming Tracks", which
  will save the current status of the upcoming playlist on exit.

This is a rather sizeable re-organization/addition of code, so if you
experience crashes/bugs in the next few days, PLEASE report them, and you can
probably assume it's my fault. =D

This feature will probably be tweaked over the next few days as well, but I
wanted to get it out there for testing.

I'm closing bug 63260 since this implements the feature.  If you'd like to
quibble on the specifics, feel free to continue commenting on the bug, I'll add
myself to the CC: list for it.

CCMAIL:63260-done@bugs.kde.org

svn path=/trunk/kdemultimedia/juk/; revision=338993