CLEAN: ConstraintAnimationLoop code related to doubleBuffer
CLEAN: ConstraintAnimationLoop code related to doubleBuffer

Former-commit-id: 9d575c168028d063c3ff066aaee733eda23a36a4
hdeling/sofa,hdeling/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,Anatoscope/sofa,Anatoscope/sofa,Anatoscope/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa