Scale: Constructor: Remove the default parameter value.
Scale: Constructor: Remove the default parameter value.

* gtk/src/scale.hg: Because we already have a default constructor,
  and this made it ambiguous.
  Bug #707810 (cheshirekow)

johne53/MB3Gtkmm,johne53/MB3Gtkmm,GNOME/gtkmm,GNOME/gtkmm,GNOME/gtkmm,GNOME/gtkmm,johne53/MB3Gtkmm