[pygtk] adding gdk functions

[Scott F. Johnston]

Yes, it's possible to add some more routines by adding
the proper prototypes.

I've added a few myself:

  (define-func gdk_window_clear_area
    none
    ((GdkDrawable drawable)
     (int x) (int y)
     (int width) (int height)))

  (define-func gdk_input_set_mode
    int
    ((uint deviceid) (GdkInputMode mode)))

  (define-func gdk_string_width
    int
    ((GdkFont font) (string text)))

Not all routines are this easy to add, however. Some will require code.