CROSS.WAD - An example of a new level.

This is a very simple level; square room with four small corridors leading
off it. Designed for deathmatch (the more players the better).

It's small because it was designed by hand.  (And building node trees really
isn't that much fun).  After I made it I realised that there wasn't any way
to leave the level so I made a wall with switches in that end the level
