Added per-stepper API for GtkRange's stepper sensitivity as discussed in

Added per-stepper API for GtkRange's stepper sensitivity as discussed in

2005-11-11  Michael Natterer  <mitch@imendio.com>

	Added per-stepper API for GtkRange's stepper sensitivity as
	discussed in bug #321056:

	* gtk/gtkenums.h: added GtkSensitivityType which can be
	{ AUTO, ON, OFF }.

	* gtk/gtkrange.[ch]: added properties "lower-stepper-sensitivity"
	and "upper-stepper-sensitivity" and public getters/setters for
	them. Changed stepper drawing to honor the new properties.

	* gtk/gtk.symbols: added the new symbols.