Add Zeek version check as well

[georgemakrakis]

In the zeek_init() event add something like the following, so it can run only for the tested versions.

if ( ! Version::at_least("7.1.1") ) {
        print fmt("Unsupported Zeek version: %s. Please use Zeek 7.1.1 or newer.", Version::number);
        return;
    }