Kill percentage flag used for -nomonsters and respawning

The Commander Keen object, which only appears in Vanilla Doom on MAP32: Grosse (Doom II), is tagged as a monster (probably mistakenly). Deathmatching with the -nomonsters command line argument causes Keen not to appear. Because killing the four Keens 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. In addition, the normal exit can be accessed by rocket jumping.