Bug#807120: Deprecate mod_rpaf, transition to mod_remoteip

[Sergey B Kirpichev <skirpichev@gmail.com>]

Package: apache2
Severity: important

mod_rpaf module has dead upstream (there are alternative
at https://github.com/gnif/mod_rpaf/) and has a good
candidate for replacement in the core modules:
http://httpd.apache.org/docs/2.4/mod/mod_remoteip.html

Probably, we must coordinate transition from mod_rpaf
to mod_remoteip and then remove mod_rpaf.

Default rpaf.conf could be replaced with:
<IfModule remoteip_module>
  RemoteIPHeader X-Forwarded-For
  RemoteIPTrustedProxy 127.0.0.1
</IfModule>
In general, this mapping should work:
  RPAFheader <-> RemoteIPHeader
  RPAFproxy_ips <-> RemoteIPTrustedProxy

To get CLF-type logs with proper client addresses we should use %a
instead of %h.  Could we alter the default common log format entry?