Remove Cautics effect

It's not used anywhere and I have no way to test it so it's useless.
Factorize code drawing shadows.
Do some cleaning
Forget to remove some unused shaders.
Fix compile
Fix for shadows.
Fix attempt for linux
Forget a hunk
Forget another change
Fix attempt for intel mesa
Avoid freeing potentially uninitialised variable.
Merge branch 'master' of https://github.com/supertuxkart/stk-code into devel