Don't listen on port or set NameVirtualHost for non-existent vhost

Apache should not listen on ports or define NameVirtualHost directives
for which there is no virtual host defined. Discussed in isse #465.
Add mod_rpaf support

From apt-cache show libapache2-mod-rpaf:

Rpaf is short for reverse proxy add forward. It changes the remote
address of the client visible to other Apache modules when two
conditions are satisfied. First condition is that the remote client is
actually a proxy that is defined in httpd.conf. Secondly if there is an
incoming X-Forwarded-For header and the proxy is in its list of known
proxies it takes the last IP from the incoming X-Forwarded-For header
and changes the remote address of the client in the request structure.
added FreeBSD support to mod_rpaf
Merge pull request #470 from antaflos/no_listen_namevirtualhost_without_vhost

Don't listen on port or set NameVirtualHost for non-existent vhost
Merge pull request #471 from ptomulik/mod_rpaf_support

Mod rpaf support (with FreeBSD support)
Merge pull request #1 from puppetlabs/master

Merge upstream changes