Added support for reading and writing the third creature flag group,
t_creaturflags3 (the offest already exists in Memory.xml). So far I've
only figured out three of the flags (out of an apparent 13):
1) announce_titan, which causes the creature to be announced as if
it was a titan or FB which had just arrived.
2) scuttle, which causes the creature to be die like it had been
killed in the game. That is, it leaves behind a corpse, and
will generate unhappy thoughts in dwarves if approriate.
3) ghostly, for creatures which are the ghosts of dead dwarves.
I updated creaturemanager to use scuttle for --kill, and added the
action --erase to kill in the old way which doesn't leave a corpse or
creatre unhappy thoughts.