wireshark: bump to version 1.12.6

- Bump to version 1.12.6
- Update hash file

The following vulnerabilities have been fixed in 1.12.6:

 - wnpa-sec-2015-19
   WCCP dissector crash. (Bug 11153)
 - wnpa-sec-2015-20
   GSM DTAP dissector crash. (Bug 11201)

[Thomas: indicate that this is a security related updated in the
commit log, as suggested by Gustavo.]

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>