Update trajectory generation to avoid using getter if it is not required.
Update trajectory generation to avoid using getter if it is not required.

	* share/urbi/trajectory-generator.u
	  (getStartValue): New, extracted from init.
	  (init): Only call getStartValue if the generator needs it.
	  (sinGet): Be lazy to avoid calling the getter.

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