apache 2.4 support
Apache 2.4 has significant changes in the auth module API:
https://httpd.apache.org/docs/trunk/developer/new_api_2_4.html
examples of how other auth modules have adapted:
https://github.com/osteenbergen/mod_auth_openid/commit/895429c85cd75fab6c87817b06518fbb4b6ecc42 https://github.com/klausdieterkrannich/mod_auth_cas/commit/4a2486746a207cb25ed2b25273899335e0309579