Integer Overflow and incompatibility with Boom's scrolls

[entryway]

1. Even with «boom (strict)» compatibility position of the blue armor after teleporting is not the same as in Boom (on the center). Shouldn't it?
2. After opening the door on the test level from the attach ZDoom crashes within ~2 minutes with Integer Overflow message. GZDoom does not.

[Graf Zahl]

I couldn't reproduce the crash - integer overflow notrmally can't happen unless there's a problem with the CPU - but the position issue is interesting:

It does get placed correctly, there's just a small issue with the order in which things get done:

- The move is too fast so it gets split in two.
- The first half of the move performs the teleport
- The second half of the move never realizes that the situation has changed and still does its thing.

Of course the direction it tries to move the armor in is wrong now. Since cause and effect are quite separated in the code this is going to be tricky...
The entire movement splitting in P_XYMovement seems to run bad if a move is blocked the first time around but in most cases the results are barely noticable.

[Graf Zahl]

fixed, since this also affected angle-changing portals it just became far more important to be addressed.