Update tcpdump to 4.9.2

It contains many fixes, including bounds checking, buffer overflows (in
SLIP and bittok2str_internal), buffer over-reads, and infinite loops.

One other notable change:

Do not use getprotobynumber() for protocol name resolution.
Do not do any protocol name resolution if -n is specified.

Submitted by: gordon
Reviewed by: delphij, emaste, glebius
MFC after: 1 week
Relnotes: Yes
Security: CVE-2017-11108, CVE-2017-11541, CVE-2017-11542
Security: CVE-2017-11543, CVE-2017-12893, CVE-2017-12894
Security: CVE-2017-12895, CVE-2017-12896, CVE-2017-12897
Security: CVE-2017-12898, CVE-2017-12899, CVE-2017-12900
Security: CVE-2017-12901, CVE-2017-12902, CVE-2017-12985
Security: CVE-2017-12986, CVE-2017-12987, CVE-2017-12988
Security: CVE-2017-12989, CVE-2017-12990, CVE-2017-12991
Security: CVE-2017-12992, CVE-2017-12993, CVE-2017-12994
Security: CVE-2017-12995, CVE-2017-12996, CVE-2017-12997
Security: CVE-2017-12998, CVE-2017-12999, CVE-2017-13000
Security: CVE-2017-13001, CVE-2017-13002, CVE-2017-13003
Security: CVE-2017-13004, CVE-2017-13005, CVE-2017-13006
Security: CVE-2017-13007, CVE-2017-13008, CVE-2017-13009
Security: CVE-2017-13010, CVE-2017-13011, CVE-2017-13012
Security: CVE-2017-13013, CVE-2017-13014, CVE-2017-13015
Security: CVE-2017-13016, CVE-2017-13017, CVE-2017-13018
Security: CVE-2017-13019, CVE-2017-13020, CVE-2017-13021
Security: CVE-2017-13022, CVE-2017-13023, CVE-2017-13024
Security: CVE-2017-13025, CVE-2017-13026, CVE-2017-13027
Security: CVE-2017-13028, CVE-2017-13029, CVE-2017-13030
Security: CVE-2017-13031, CVE-2017-13032, CVE-2017-13033
Security: CVE-2017-13034, CVE-2017-13035, CVE-2017-13036
Security: CVE-2017-13037, CVE-2017-13038, CVE-2017-13039
Security: CVE-2017-13040, CVE-2017-13041, CVE-2017-13042
Security: CVE-2017-13043, CVE-2017-13044, CVE-2017-13045
Security: CVE-2017-13046, CVE-2017-13047, CVE-2017-13048
Security: CVE-2017-13049, CVE-2017-13050, CVE-2017-13051
Security: CVE-2017-13052, CVE-2017-13053, CVE-2017-13054
Security: CVE-2017-13055, CVE-2017-13687, CVE-2017-13688
Security: CVE-2017-13689, CVE-2017-13690, CVE-2017-13725
Differential Revision: https://reviews.freebsd.org/D12404