Fix compiler warnings (button-widget.c)
Fix compiler warnings (panel-util.c, panel.c, xstuff.c)
Fix all compiler warnings in panel-properties-dialog.c
Fix all warning except GCompletion in panel-run-dialog.c
Fix compiler warnings (menu.c) Now no images in main menu.
Partially revert prev to show images in menus.
Fix compiler warnings in panel-context-menu.c (except GtkImageMenuItem)