Add cmake helper files for finding wireshark

These files make it possible to use the cmake command find_package(Wirehark) to obtain information about the wireshark installation.

Change-Id: I5af7c4e7b53b99cd473e04905a92bac267cd9b83
Reviewed-on: https://code.wireshark.org/review/5235
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>