Here, we weren't recognizing that the template parameter of A is used by the
reference to d in the requires-clause of f.  Fixed by passing down the
active template parameters in the context of normalization, and adding to
the mapping any such parameters shared by a member template used in the
constraint-expression.

	* pt.c (struct find_template_parameter_info): Add ctx_parms.
	(any_template_parm_r): Handle TEMPLATE_DECL.
	(find_template_parameters): Take parms instead of their depth.
	* constraint.cc (build_parameter_mapping): Pass them.