Raises latejoiner antag cap slighty and ports /tg/'s lower cap.

Lower cap code by Ikarrus!
There's some modifications by me aswell.

This should help make rounds less boring, especially with lots of latejoiners. If the ideal crewmember:antag ratio gets too low, the next latejoiner is guaranteed to become an antag. Works in traitor, traitorchan and changeling rounds.

I also raised the upper cap a bit. Previously, the upper cap was... at the ideal crew:antag ratio. Now there's a bit of room upwards too.