Small housekeeping work in gigi

Small housekeeping work in gigi

No functional changes.

	* gcc-interface/gigi.h (change_qualified_type): Move around.
	(maybe_vector_array): Likewise.
	(maybe_padded_object): New static line function.
	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Component_Size>:
	Remove useless code.
	<Attr_Null_Parameter>: Remove obsolete code.
	(Call_to_gn): Likewise.  Use maybe_padded_object to remove padding.
	(gnat_to_gnu): Likewise.
	<N_String_Literal>: Do not add a useless null character at the end.
	<N_Indexed_Component>: Likewise and remove obsolete code.
	(add_decl_expr): Likewise.
	(maybe_implicit_deref): Likewise.
	* gcc-interface/utils.c (maybe_unconstrained_array): Likewise.
	* gcc-interface/utils2.c (gnat_invariant_expr): Likewise.