WIP:Fixes related to P_CheckDeathPitCollide checks

Prevents objects that are dead, have MF_NOCLIPHEIGHT, or have MF2_BOSSDEAD from getting eaten by death pits. Also removes the redundancy that making several different special cases for colliding with a pit that were the exact same had.

Fixes a visual bug that would occur when Tails walks onto a death floor. His tails followmobj would spazz out since it was constantly being removed and respawned.

Improves Lua support by allowing coders to give their objects MF_NOCLIPHEIGHT or MF2_BOSSDEAD to prevent death pit removal.

Also fixes bosses not being properly killed when they collide with a death pit.

However, not everything has been tested yet, and beating the Egg Slimer or Fang bosses has a tendency to crash the game. Haven't been able to fix it myself yet due to my version of the game not being able to create debug files for whatever reason. Will try and look more into the bugs later.