Implement C++11 inheriting constructors.

	* cp-tree.h (cpp0x_warn_str): Add CPP0X_INHERITING_CTORS.
	(DECL_INHERITED_CTOR_BASE, SET_DECL_INHERITED_CTOR_BASE): New.
	(special_function_kind): Add sfk_inheriting_constructor.
	* class.c (add_method): An inheriting ctor is hidden by a
	user-declared one.
	(one_inheriting_sig, one_inherited_ctor): New.
	(add_implicitly_declared_members): Handle inheriting ctors.
	* error.c (maybe_warn_cpp0x): Handle CPP0X_INHERITING_CTORS.
	* init.c (emit_mem_initializers): Don't set LOOKUP_DEFAULTED
	for an inheriting constructor.
	* method.c (type_has_trivial_fn): Handle sfk_inheriting_constructor.
	(type_set_nontrivial_flag): Likewise.
	(add_one_base_init): Split out from...
	(do_build_copy_constructor): ...here.  Handle inheriting constructors.
	(locate_fn_flags): Handle a list of arg types.
	(synthesized_method_walk): Handle inheriting constructors.
	(maybe_explain_implicit_delete): Likewise.
	(deduce_inheriting_ctor): New.
	(implicitly_declare_fn): Handle inheriting constructors.
	* name-lookup.c (push_class_level_binding_1): An inheriting constructor
	does not declare the base's name.
	(do_class_using_decl): Allow inheriting constructors.
	* pt.c (template_parms_to_args): Split from current_template_args.
	(add_inherited_template_parms): New.
	(tsubst_decl): Handle inheriting constructors.
	* tree.c (special_function_p): Handle inheriting constructors.

Co-Authored-By: Ville Voutilainen <ville.voutilainen@gmail.com>

From-SVN: r192448