Dead code in ip6_savecontrol: RTHDRDSTOPTS walk result discarded, RFC3542 semantics not implemented

Summary

Block guarded by IN6P_DSTOPTS|IN6P_RTHDRDSTOPTS(:1173) walks ext-header chain via ip6_nexthdr(:1188-1199) to locate Routing header. Variables proto/off/nxt declared local(:1175), loop result never stored. Subsequent block(:1202-1320) re-walks from scratch treating every DSTOPTS header identically. RFC3542 pre-RH (RTHDRDSTOPTS) vs post-RH (DSTOPTS) distinction not implemented. Socket requesting RTHDRDSTOPTS receives nothing; socket requesting DSTOPTS receives both. RFC non-conformance, no security impact.