Regenerate signals/properties defs.

* clutter/src/clutter_signals.defs: Regenerated with
  codegen/gen_scripts/clutter_generate_signals.defs
PathConstraint: Correct the signa.

* clutter/src/path-constraint: The node-reached signal sends a
  guint, not an int, and it cannot have a default signal handler
  because the struct is hidden.