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.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@249088 138bc75d-0d04-0410-961f-82ee72b054a4