Fix bug 88847 (Previous track doesn't work anymore in Play Queue mode).  This was actually by design, as items in the upcoming playlist are so ephemeral that keeping track of them would later crash JuK.  However, instead the associate collection list item is stored instead, which I feel is a better alternative.

BTW to the reporter, JuK doesn't actually use the history playlist for this. ;-)

CCMAIL:88847-done@bugs.kde.org

svn path=/trunk/kdemultimedia/juk/; revision=344076