Changed wizards' speed and radius so that they don't fire while outside the screen

Wizards can now get a second shot in if the player is moving slowly or
is hit by something (e.g. the first shot). Previously they almost never
got that second shot away before the player was gone.
Added new chunk type

Added a chunk with one long platform below and short platforms a bit
up. Reachable by double jump or, with luck, by bat.
Fireballs don't make sound when hitting platforms

The fireballs are often outside the screen when they hit platforms, so
we don't want a sound for that.