Implement GL_ELAPSED_TIME query

This allows to measure gpu execution time very accurately.
Do not built grass shadow shader
Initial work to port GP win/lose cutscenes to new system
Add DOF checkbox to the graphics options
Fix attempt for #1308
Tweak light extend.
Work on GP end cutscene
More work on porting GP win scene
Work on new GPWin screen. Seems to work well now
Merge branch 'NewGPCutscene'
Merge branch 'master' of https://github.com/supertuxkart/stk-code
Use a more tighly fitting quad for pointlights.
Simplify pointlight.vert
Unload texture transformation state cache.
Work on cutscenes
Merge branch 'master' of https://github.com/supertuxkart/stk-code
Tweak light extent again to improve perf
Merge branch 'master' of https://github.com/supertuxkart/stk-code