Allow deduction guides to look into primary template.

Allow deduction guides to look into primary template.

	* cp-tree.h (struct saved_scope): Add deduction_guide_type.
	(struct cp_decl_specifier_seq): Add constructor_p.
	* parser.c (cp_parser_decl_specifier_seq): Set constructor_p.
	(cp_parser_init_declarator): Check it.  Set ctor_dtor_or_conv_p.
	Clear deduction_guide_type.  Don't handle deduction guide names.
	(cp_parser_declarator): Don't clear ctor_dtor_or_conv_p.
	(cp_parser_direct_declarator): Likewise.  Handle deduction guides.
	(cp_parser_member_declaration, cp_parser_cache_defarg)
	(cp_parser_objc_class_ivars): Set ctor_dtor_or_conv_p.
	* pt.c (tsubst_copy, tsubst_copy_and_build): Revert last change.
	(build_deduction_guide): Set deduction_guide_type.
	(dependent_scope_p): Check deduction_guide_type.
	* search.c (lookup_member): Likewise.

From-SVN: r245858