wireshark: bump version to 2.2.6 (security)

wireshark: bump version to 2.2.6 (security)

Security fixes:

- wnpa-sec-2017-12
  IMAP dissector crash (Bug 13466) CVE-2017-7703
- wnpa-sec-2017-13
  WBMXL dissector infinite loop (Bug 13477) CVE-2017-7702
- wnpa-sec-2017-14
  NetScaler file parser infinite loop (Bug 13478) CVE-2017-7700
- wnpa-sec-2017-15
  RPCoRDMA dissector infinite loop (Bug 13558) CVE-2017-7705
- wnpa-sec-2017-16
  BGP dissector infinite loop (Bug 13557) CVE-2017-7701
- wnpa-sec-2017-17
  DOF dissector infinite loop (Bug 13453) CVE-2017-7704
- wnpa-sec-2017-18
  PacketBB dissector crash (Bug 13559)
- wnpa-sec-2017-19
  SLSK dissector long loop (Bug 13576)
- wnpa-sec-2017-20
  SIGCOMP dissector infinite loop (Bug 13578)
- wnpa-sec-2017-21
  WSP dissector infinite loop (Bug 13581)

Full release notes:

  https://www.wireshark.org/docs/relnotes/wireshark-2.2.6.html

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>