supertux: Update to 0.6.0

- Complete redesign of the icy world and forest world (Thank you,
RustyBox and Serano)

- Complete revamp of our rendering engine, the game should be much
faster than it was previously

- We now support OpenGL 3.3 Core as well as OpenGL ES 2.0, thus
allowing SuperTux to be run on the Raspberry Pi, and potentially
WebGL.

- Support for right-to-left languages through vector fonts. This
will also fix a few non-ASCII characters, which often caused problems
before in translations

- A lot of other under-the-hood changes and bugfixes

A few graphics have been updated, and effects have been added:

- The save bell was reworked (Thanks to Raghavendra ���raghukamath���
Kamath!)

- Improved big Tux graphics and animations (Thanks to Alzter)

- Various effects and shaders (Thanks to Grumbel)

(nia)