re PR c++/14199 (Unjustified warning about unused variable)

re PR c++/14199 (Unjustified warning about unused variable)

	PR c++/14199
	* pt.c (tsubst_copy): Call mark_used for a PARM_DECL.

	PR c++/14173
	* semantics.c (begin_class_definition): Set TYPE_PACKED correctly
	for all type variants.

	PR c++/14173
	* g++.dg/ext/packed5.C: New test.

	PR c++/14199
	* g++.dg/warn/Wunused-5.C: New test.

	PR c++/13927
	* decl.c (duplicate_decls): Return error_mark_node for invalid
	redeclarations.
	* name-lookup.c (push_namespace): Ignore the return value from
	pushdecl.
	* pt.c (push_template_decl_real): Robustify.

	PR c++/13927
	* g++.dg/other/error8.C: Remove XFAIL markers.

From-SVN: r78159