It'd be nice if there were setters for the GtkAdjustment fields.  If I
read the gtk doco right, it's normal for a program to mung them and
call gtk_adjustment_changed when wanting a new page size or whatever.

For the value field I guess there's gtk_adjustment_set_value, so
perhaps there's no need to directly set that, but apparently it's
valid to do so and later call gtk_adjustment_value_changed.

I get some joy from the diff below, if this is the right way to go
about it.

        * gtk-1.2.defs (GtkAdjustment): Add setters for the fields.