Change the plugin compatibility check to make it more convenient to
define and check the major.minor Wireshark version.
Change-Id: I2a6d2a746682c29504311cce5c457e0a852c3daf
Reviewed-on: https://code.wireshark.org/review/29224
Petri-Dish: João Valverde <j@v6e.pt>
Tested-by: Petri Dish Buildbot
Reviewed-by: João Valverde <j@v6e.pt>