Here is a sample XKeyboard Definition to include inside the Keyboard Section of your XF86Config File.
    Xkbkeycodes "xfree86"
/*    XkbSymbols  "us(pc101)+de_nodead"  */
/*    This has changed between 3.1.2E and 3.1.2F */
/*    it is now:                                 */
    XkbSymbols  "us(pc102)+de(nodeadkeys)"
    XkbTypes    "default"
    XkbCompat   "default"
    XkbGeometry "pc"
or you could use this one with the new Options:
XkbRules "xfree86" XkbModel "pc102" XkbLayout "de" XkbVariant "nodeadkeys"