* cp-tree.def (OFFSETOF_EXPR): New.

        * parser.c (cp_parser_builtin_offsetof): Either built an
        OFFSETOF_EXPR, or call fold_offsetof immediately.
        * pt.c (tsubst_expr): Handle OFFSETOF_EXPR.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@86679 138bc75d-0d04-0410-961f-82ee72b054a4