parser: use container ctors that accept initial members.
parser: use container ctors that accept initial members.

	* src/parser/ugrammar.y: here.
	Suggested by Roland Levillain.
	Use <<.
	(formal_argument, formal_arguments, formal_arguments.1): rename
	as...
	(formal, formals.0, formals.1): these.

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