PR c++/17011, c++/17971
	* pt.c (tsubst_copy) <FIELD_DECL case>: Check and diagnose
	invalid field.
	(tsubst_copy_and_build) <COMPONENT_REF case>: Check
	error_mark_node after member substitution.
	* semantics.c (finish_id_expression): Call
	finish_non_static_data_member for non-dependent FIELD_DECL.

	* g++.dg/template/error15.C: Adjust expected error.
	* g++.dg/template/instantiate3.C: Likewise.

From-SVN: r91720