Clean some #define
Use non debug gl ctx in non debug build
Factorize matrix block uniform assignment
Add some documentation to add new material.
Try to fix OSX
Disable all extension on OSX

OSX does support GL 4.1 + a couple of 4.2 extensions. Since not all 4.2
extensions are present, disable extensions support instead of supporting
several combinaisons of extensions.
Inverted logic for compute shaders
Show "?" if a track has no screenshot (instead of the screenshot of
the previous track).
Fix particle for hd3000
Merge branch 'master' of github.com:supertuxkart/stk-code
Remove unneeded if (version/glcap) in shader ctor
Fix LOD
Merge branch 'master' of https://github.com/supertuxkart/stk-code
Move texture management function in a separate file.
Forgot to fix a particle shader for hd3000
Revert "Forgot to fix a particle shader for hd3000"

This reverts commit 48fcea8ee8fba01e3def8f3117214d3f92f33872.
Properly reapply HD3000 particle fix
Inverse updateAbsolutePosition and Visibility test in scenemanager
Start to support driving (and rescuing) on physical track objects.
Merge branch 'master' of github.com:supertuxkart/stk-code