AVALANCHE: Repair the ghost's animation.

Now it doesn't overlap with the bat's static picture on the bottom of
the screen.
AVALANCHE: Add the yelling to the end of the ghost's animation.
AVALANCHE: Implement the ghostroom's animation until Avvy turns back.
AVALANCHE: Implement another pair of floating eyeballs.

Repair the previous one.
AVALANCHE: Finish GhostRoom's implementation.
AVALANCHE: Repair GhostRoom::doBat().