re PR c++/66260 ([C++14] Failure to compile variable template with recursively defined partial specialization)

	PR c++/66260
	PR c++/66596
	PR c++/66649
	PR c++/66923
	* pt.c (lookup_template_variable): Use NULL_TREE for type.
	(instantiate_template_1): Also set DECL_TI_ARGS based on
	the immediate parent.
	(tsubst_copy_and_build) [TEMPLATE_ID_EXPR]: Handle variable templates.
	(finish_template_variable): Add complain parm.
	* cp-tree.h: Adjust.

From-SVN: r226642