package/wireshark: security bump to version 2.6.6

package/wireshark: security bump to version 2.6.6

Fixes the following security vulnerabilities:

- wnpa-sec-2019-01 The 6LoWPAN dissector could crash. Bug 15217. CVE-2019-5716
  https://www.wireshark.org/security/wnpa-sec-2019-01

- wnpa-sec-2019-02 The P_MUL dissector could crash. Bug 15337. CVE-2019-5717
  https://www.wireshark.org/security/wnpa-sec-2019-02

- wnpa-sec-2019-03 The RTSE dissector and other dissectors could crash.  Bug
  15373.  CVE-2019-5718
  https://www.wireshark.org/security/wnpa-sec-2019-03

- wnpa-sec-2019-04 The ISAKMP dissector could crash. Bug 15374. CVE-2019-5719
  https://www.wireshark.org/security/wnpa-sec-2019-04

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>