gtk3: set rgba visual for applets
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
Merge pull request #195 from dnk/applet_rgba_visual

gtk3: set rgba visual for applets
Merge pull request #4 from mate-desktop/master

Merge from master