Create a sniff to make sure we are not using filter_input for server variables

[atimmer]

Filtering SERVER_INPUT variables using filter_input is disabled on some PHP configurations. (And fails silently)

[atimmer]

Wrong:

$value = filter_input( INPUT_SERVER, 'any-value' );

Correct:

$value = $_SERVER[ 'any-value' ];

This probably also requires sanitisation, because that is normally covered by filter_input but I am assuming that another rule covers sanitisation.