Preparing lens flare branch
Add the lensflare shader
Merge branch 'master' of https://github.com/supertuxkart/stk-code into lensflare

Keep lens flare updated with master
minor modification to the blueish mood of lens flare
Merge branch 'master' of https://github.com/supertuxkart/stk-code into lensflare

Keep lens flare updated with trunk
Merge branch 'master' of https://github.com/supertuxkart/stk-code into lensflare

keep compatibility with master
Merge branch 'master' of https://github.com/supertuxkart/stk-code into lensflare
Merge branch 'master' of https://github.com/supertuxkart/stk-code into lensflare
Merge branch 'master' of https://github.com/supertuxkart/stk-code into lensflare
Use variable sigma for blur filter
Change fog equation
Use fog start value to determine density
Added more asserts.
Fixed compiler warnings.
tweak value
Merge branch 'master' of github.com:supertuxkart/stk-code
Implement scattering for point light
Fix classic fog
merge with trunk + try to adapt to the new blur system
Try to tweak the lens flare without being too obvious