mkdir

static VALUE
path_mkdir(int argc, VALUE *argv, VALUE self)
{
 VALUE str = get_strpath(self);
 VALUE vmode;
 if (rb_scan_args(argc, argv, "01", &vmode) == 0)
 return rb_funcall(rb_cDir, id_mkdir, 1, str);
 else
 return rb_funcall(rb_cDir, id_mkdir, 2, str, vmode);
}