fix duplicate entry in ruleset
fix visibility in smoke
double check that math.

again, thanks to bresenham doubling, this is some confusing stuff, but this
multiplication throws the formula off in our case.
zombify units BEFORE endturn
fix some offscreen behaviour.
silly warboy, setting a bad example.
add safety to turning
charge TUs before first step

handily, that bool already existed.
fix some death bugs

stop falling corpses from turning their comrades invisible.
don't draw weapons on dying chryssalids.
account for strafe in "first move" determination.
fix large unit gravity

by not allowing it.
hahaha whoops.
derp, flying units.
Adjust crash site and landing site numbering.
fix units going off-screen and bringing the game to a halt