qt4: add tooltip to playlist viewchange-button

(cherry picked from commit 990437d4a5ef58caeb0ec0ef8cd1bdd37710cd25)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/playlist/standardpanel.cpp

@@ -96,6 +96,7 @@ StandardPLPanel::StandardPLPanel( PlaylistWidget *_parent,
     /* Button to switch views */
     QToolButton *viewButton = new QToolButton( this );
     viewButton->setIcon( style()->standardIcon( QStyle::SP_FileDialogDetailedView ) );
+    viewButton->setToolTip( qtr("Change playlistview"));
     layout->addWidget( viewButton, 0, 1 );
 
     /* View selection menu */