“When one, in liege poustie , makes over his estate to his heir, with a reserved faculty to revoke or burden it, and anytime of his life afterwards exercises the faculty on deathbed, if the heir has done any act importing an acceptance of the deed in which the faculty was reserved, he cannot challenge the exercise of it upon deathbed, for his acceptance of the disposition, with its reservations and conditions, makes him disponee, and disponees have not the privilege of heirs, and, of course, have no right to bring reductions ex capite lecti. ”