Provide a Request::getRemoteAddress() to use instead of
$_SERVER['REMOTE_ADDR'] to be proxy compliant.

Security

The web server is trusted to clean headers and only forward to
the PHP processes the whitelisted headers, with validated values
or with values determines by the server.

This plays very well with scenarii like nginx front-end, nginx back-end
and php-fpm.

Ref T1395

Unit tests are provided, from rKGF