Flippety Floppety Floo: Handle icon flippedness correctly everywhere.

There was a call to flip images being rendered in ViToolbarPopUpButtonCell that
was breaking all drawing using drawAtPoint:, which we switched to in order to
avoid deprecation warnings on compositeToPoint:.

This removes all weird flippedness handling in the code and the original flip
in the final drawing component.

Fixes #84 .