Dynamic crushers

[jb0lt]

Description of the feature

Crushers should dynamically change length depending on what is in front of it, I. e. a crusher shouldn't go though the ground nor be showing though the back side of another crusher's plate.

Why should this be implemented

I don't think I want to be a player at the mercy of an inconsiderate map creator putting crushers hidden in the walls, plus it looks a lot better

Additional information

Problem to be solved: This setup a will actually kill you if you touch that wall: