re PR c++/9447 (using Base<T>::member does not work)

cp:
	PR c++/9447
	* cp-tree.def (USING_DECL): Document its type.
	* class.c (pushclass): If we're entering a template, push any
	dependent using decls it has.
	* decl2.c (do_class_using_decl): Refactor. Type is NULL iff it is
	a dependent scope.
	* pt.c (tsubst_decl) <USING_DECL case>: Set type.
	(tsubst): Remove USING_DECL checks.
	(type_dependent_expression_p): Remove USING_DECL case.
	* semantics.c (finish_member_declaration): A USING_DECL's type
	indicates whether it is dependent.
testsuite:
	PR c++/9447
	* g++.dg/template/using7.C: New test.

From-SVN: r70107