CVS commit by snel: 

Add volume slider (bugreport #58507), TODO: fix hide slider with button


  M +21 -0     playlist.xpm   1.2
  M +77 -33    userinterface.cpp   1.12
  M +8 -2      userinterface.h   1.6
  M +21 -0     volume.xpm   1.2
  R            eject.xpm   1.1