which crushing mode is used: 0 uses the game's default for compatibility,
1 uses Doom's mode (crushers continue to move while damaging any actors ) and
2 uses Hexen's mode (crushers stay at blocking actor's top until they die).
Since Generic_Crusher already used all 5 args I created a second version for
Hexen crushing mode.
- Added PICKUP flag to DECORATE.
SVN r817 (trunk)