CVS commit by snel: 

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


  A            playlist.xpm   1.1.2.1
  A            volume.xpm   1.1.2.1
  M +78 -34    userinterface.cpp   1.7.2.3
  M +8 -2      userinterface.h   1.4.2.2
  R            eject.xpm   1.1