Fix radiobutton focused state

[rdbende]

Currently the radiobutton is quite glitchy when focused. Mostly because of the changes introduced in e34864a.

Sometimes they don't render at all:

While printing a bunch of errors.

(wish:52092): Gdk-CRITICAL **: 23:05:05.778: IA__gdk_pixbuf_get_from_drawable: assertion 'src_x + width <= src_width && src_y + height <= src_height' failed

** (wish:52092): CRITICAL **: 23:05:05.778: gdk_pixbuf_xlib_render_to_drawable: assertion 'pixbuf != NULL' failed

(wish:52092): GLib-GObject-CRITICAL **: 23:05:05.778: g_object_unref: assertion 'G_IS_OBJECT (object)' failed

and with some Gtk themes it looks like this:

This patch fixes these bugs. I removed the focus padding stuff, and copied most parts of the checkbutton code, which works well.