c++: NTTP type CTAD w/ tmpl from current inst [PR113649]

Since template argument coercion happens relative to the most general
template (for a class template at least), during NTTP type CTAD we might
need to consider outer arguments particularly if the CTAD template is from
the current instantiation (and so depends on outer template parameters).

This patch makes do_class_deduction substitute as many levels of outer
template arguments into a CTAD template (from the current instantiation)
as it can take.

	PR c++/113649

gcc/cp/ChangeLog:

	* pt.cc (do_class_deduction): Add outer_targs parameter.
	Substitute outer arguments into the CTAD template.
	(do_auto_deduction): Pass outer_targs to do_class_deduction.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/nontype-class65.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>