Cleaned up some junk in bonus_block.

Cleaned up some junk in bonus_block.
Removed some unnecessary switches to reduce the amount of code.  Star and Tux dolls now make a noise when leaving the bonus block.  Removed unused variable from coin_explode.  Heavy coins now bounce once when hitting the ground at high velocity and reflect their y velocity when hitting the bottome of something.  Made it easy for the editor to place bonus blocks with the flip level potions.