Deal with Passenger moving the Apache module

As best I can tell, for Passenger

    $version >= 4.0.0           ${gemdir}/buildout/apache2/mod_passenger.so
    3.9.0 <= $version < 4.0.0   ${gemdir}/libout/apache2/mod_passenger.so
    $version < 3.9.0            ${gemdir}/ext/apache2/mod_passenger.so