Upgrade code to be PHP 8 compatible

[the-r3dacted]

Seems to mostly work with 5000 warns, However there are a few major errors. Have no idea how to update it myself without breaking anything.

[the-r3dacted]

Quick bodge to make it mostly work, in thread.php, remove , " " from this line:

$pagelinks = $first.$prev.join(array_slice($pageLinks, 0, 11), " ").$next.$last;

Making it instead be:

$pagelinks = $first.$prev.join(array_slice($pageLinks, 0, 11)).$next.$last;

What this does I have no idea, but thread pages work in PHP 8 now. Won't commit it to repo since no idea if it breaks anything else.

[the-r3dacted]

Edit profile page does not work, applying the changes just takes you to a blank page with the footer in plaintext.