clock: Dont use deprecated rsvg_pixbuf_from_file_at_size

This required to copy some code from GTK3 source to make it working with GTK2 too

Thanks to Sander Sweers for the help to replace rsvg_pixbuf_from_file_at_size
gtk3: set rgba visual for applets
Fix non-expanded panels (Vertical)
Fixed all issues on non-expanded panels, except for wnck-applet (window
list).
Fixed window list.