- Added A_Remove(int pointer, int flags).

- RMVF_MISSILES removes missiles.
- RMVF_NOMONSTERS ignores monsters.
- RMVF_MISC includes non-monsters and missiles.
- RMVF_EVERYTHING disregards all checks and remove it.

These flags now apply to the following in addition to the new function:

-A_RemoveTarget
-A_RemoveMaster
-A_RemoveTracer
-A_RemoveChildren
-A_RemoveSiblings