C++ cleanups before C++17 noexcept in types.

C++ cleanups before C++17 noexcept in types.

	* call.c (standard_conversion): Reorganize pointer conversions.
	* pt.c (convert_nontype_argument_function): Convert to ref here.
	(convert_nontype_argument): Not here.
	(convert_template_argument): Add original type to error message.
	(RECUR_AND_CHECK_FAILURE): Remove trailing semicolon.
	(unify): Compare function-qualifiers.
	* typeck.c (same_type_ignoring_top_level_qualifiers_p): Use
	cp_build_qualified_type rather than TYPE_MAIN_VARIANT.

From-SVN: r241943