Slight update to ThiefRL2

I had a little bit of time over the holidays so I fixed a couple of bugs in ThiefRL 2 that show up in rare circumstances.

When a guard was moving to the player's last known position, if the player moved into their path they'd move on top of the player. This has been fixed.

When there were windows adjacent to both sides of the corner of a room, the corner would not be visible from that room. I kind of hacked in the one-way visibility for the windows and it had some unintended side effects. I completely overhauled the visibility portal system which was incredibly boring but it now supports one-way portals, making the hacks unnecessary.

Guards now turn to face noises, which makes noises more risky than they were. Previously you pretty much had to just not make two noises in a row and you were fine.

Finally, I experimented with having guys face in the direction of their intended next move, instead of facing the direction of their last move. It looked weird though so I left it out.