c++: Check satisfaction before non-dep convs. [CWG2369]

c++: Check satisfaction before non-dep convs. [CWG2369]

It's very hard to use concepts to protect a template from hard errors due to
unwanted instantiation if constraints aren't checked until after doing all
substitution and checking of non-dependent conversions.

It was pretty straightforward to insert the satisfaction check into the
logic, but I needed to make the 3-parameter version of
satisfy_declaration_constraints call push_tinst_level like the 2-parameter
version already does.  For simplicity, I also made it add any needed outer
template arguments from the TEMPLATE_DECL to the args.

The testsuite changes are mostly because this change causes unsatisfaction
to cause deduction to fail rather than reject the candidate later in
overload resolution.

gcc/cp/ChangeLog:

	DR 2369
	* cp-tree.h (push_tinst_level, push_tinst_level_loc): Declare.
	* constraint.cc (satisfy_declaration_constraints):
	Use add_outermost_template_args and push_tinst_level.
	* pt.c (add_outermost_template_args): Handle getting
	a TEMPLATE_DECL as the first argument.
	(push_tinst_level, push_tinst_level_loc): No longer static.
	(fn_type_unification): Check satisfaction before non-dependent
	conversions.

gcc/testsuite/ChangeLog:

	DR 2369
	* g++.dg/concepts/diagnostic10.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic13.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic2.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic3.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic4.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic5.C: Adjust expexcted errors.
	* g++.dg/concepts/diagnostic9.C: Adjust expexcted errors.
	* g++.dg/concepts/expression2.C: Adjust expexcted errors.
	* g++.dg/concepts/fn5.C: Adjust expexcted errors.
	* g++.dg/concepts/placeholder5.C: Adjust expexcted errors.
	* g++.dg/concepts/pr67595.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-pr78752-2.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-pr84140.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-recursive-sat3.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-requires18.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-requires19.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts3.C: Adjust expexcted errors.
	* g++.dg/cpp2a/concepts-nondep1.C: New test.
	* g++.dg/cpp2a/concepts-nondep1a.C: New test.