Stop using filter_input with $_SERVER variables

[shadyvb]

Because of a PHP confirmed bug, filter_input( INPUT_SERVER, 'anything' ) would return null on some implementations of FCGI/PHP 5.4 ( and probably older versions as well ).
https://bugs.php.net/bug.php?id=49184

Use workaround mentioned in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=730094:

if (filter_has_var(INPUT_SERVER, "SERVER_NAME")) {
        $servername = filter_input(INPUT_SERVER, "SERVER_NAME",
FILTER_UNSAFE_RAW, FILTER_NULL_ON_FAILURE);
    } else {
        if (isset($_SERVER["SERVER_NAME"]))
            $servername = filter_var($_SERVER["SERVER_NAME"],
FILTER_UNSAFE_RAW, FILTER_NULL_ON_FAILURE);
        else
            $servername = null;
    }

Reported at https://wordpress.org/support/topic/ip-addresses-not-showing-being-added-to-db-in-version-119?replies=9

[frankiejarrett]

@shadyvb How obscure! Good on ya.

[westonruter]

Interesting. Yeah, and Nacin said that the filter_* functions aren't allowed in core because of un-guaranteed availability. I've removed them from Widget Customizer.

[shadyvb]

That's just sad :(

[jonathanbardo]

Good to know. It's a shame they are not super reliable. Should we try to avoid them in the future @westonruter?

[westonruter]

@jonathanbardo yeah, unfortunately I think we can't rely on them if they aren't reliable for core.

[frankiejarrett]

Sorry I must have closed this by accident! Fail