Overhaul pointer-to-member conversion and template argument handling.

Overhaul pointer-to-member conversion and template argument handling.

	* call.c (standard_conversion): Avoid creating ck_pmem when the
	class type is the same.
	* cvt.c (can_convert_qual): Split from
	perform_qualification_conversions.
	* constexpr.c (cxx_eval_constant_expression): Check it.
	* typeck.c (convert_ptrmem): Only cplus_expand_constant if
	adjustment is necessary.
	* pt.c (check_valid_ptrmem_cst_expr): Compare class types.
	(convert_nontype_argument): Avoid redundant error.

From-SVN: r249088