Last crasher bug I fixed was due to not using Playlist::clearItem() to remove a PlaylistItem.  I think it
should always be possible to call delete on a PlaylistItem pointer and the Right Thing happens, so do a
bit of refactoring to ensure that what happens in clearItem() is performed from the PlaylistItem dtor instead
of running the PlaylistItem dtor from clearItem.

svn path=/trunk/KDE/kdemultimedia/juk/; revision=926748