Made apache2-http.include.conf Apache 2.4 compatible.

Since Apache 2.4, `Require all granted` replaces the lines:
    Order allow,deny
    allow from all
This is wrapped in `<IfVersion …></IfVersion>` directives to
ensure backwards compatibility with older Apache versions than 2.4.
Merge branch 'apache-2.4' of https://github.com/eliasp/otrs
Added support for Apache 2.4 in the web server configuration file.