Kill percentage flag used for -nomonsters and respawning

The Commander Keen object, which only appears by default on MAP32: Grosse (Doom II), is (probably mistakenly) tagged as a monster. When deathmatching and using the -nomonsters command line argument, it does not appear, and as it is needed to expose the end to the level (via Tag 666), Grosse cannot be exited when using -nomonsters (unless one is also using the -timer command).

MAP07: Dead Simple (Doom II) has monsters that must be killed to access the exit, but has another exit that is only reachable via a deathmatch spawnspot, so can be exited.

MAP32:_Grosse_%28Doom_II%29