WINTERMUTE: Prevent scripts from setting invalid scroll times

Scroll times (ScrollSpeedX, ScrollSpeedY) can't be zero, as this leads
to a division by zero later on. This allows Dreamscape to start and
work properly.
FULLPIPE: Initial code for scene09
AVALANCHE: Implement Help::run().
AVALANCHE: Partially implement Help::getMe().

The drawing of the buttons are still missing.
AVALANCHE: Move/rename/implement Help::plotButton().
PEGASUS: Fix returning from Mars after destroying the robot's shuttle