Handle multi-level typenames and implicit typename in base list.
* parse.y (typename_sub{,[0-2]}): New rules.
(structsp, rule TYPENAME_KEYWORD): Use typename_sub.
(nonnested_type): New rule.
(complete_type_name): Use it.
(base_class.1): Use typename_sub and nonnested_type.
(nested_name_specifier): Don't elide std:: here.
* decl.c (make_typename_type): Handle getting a type for NAME.
(lookup_name_real): Turn std:: into :: here.
Rvalue conversions were removed in London.
* call.c (is_subseq): Don't consider lvalue transformations.
(build_conv): LVALUE_CONV and RVALUE_CONV get IDENTITY_RANK.
(joust): Reenable ?: kludge.