supertux: Update to 0.6.2

SuperTux 0.6.2 (2020-05-14)
---------------------------
The SuperTux Team is excited to announce the availability of SuperTux 0.6.2. This release fixes a number of bugs that were reported after 0.6.1. It also features reworked graphics and levels.

Other changes include a power-up counter in the hud, new sprites for the door, a new tileset and several new badguys. But overall, this release is supossed to celebrate our anniversary (May 2000) with a little surprise Add-On, which can be found in the contrib levels!

Changes:
  - A new worldmap, "Revenge In Redmond" celebrating SuperTux's 20th anniversary, which includes new enemies and sprites !!!
  - New and improved backgrounds and sprites
  - Improvements to many levels in the Icy Island and forest world
  - Speed improvements for levels using a huge amount of lava tiles
  - An issue causing the bridge in the forest world to not be shown in certain cases was fixed

(nia)