print-icmp6: remove useless break
print-802_11: cleanup handle_deauth()

- variable 'offset' is assigned a value that is never used
- parameter 'length' is updated and the new value is never used
print-forces: print_metailv(): unused parameter 'len'
print-mobile: mobile_print(): variable 'cp' is assigned a value that is never used
RRCP: remove extra return
print-pptp: pptp_result_code_print(): badly placed break
print-pptp: add a missing break
only include udp.h when necessary