Factor exceptions and compute message when used. Fix issue 3193.
Factor exceptions and compute message when used.
Fix issue 3193.

	* share/urbi/exception.u (Exception.asString): Handle slot and
	routine location.

	* share/urbi/exception.u: Factor common exception declaration
	patterns into makeException functions.  Replace message computation
	at the initialisation by members declaration and message computation
	when asked.

urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi