cgogn extlib : some minor changes in the phi2 and phi3 functions of implicit maps.
cgogn extlib : some minor changes in the phi2 and phi3 functions of implicit maps.

Signed-off-by: Étienne Schmitt <etienne.schmitt@inria.fr>

Former-commit-id: dd36d9b97f2201eabdc18819d105cbeff431d062
hdeling/sofa,hdeling/sofa,Anatoscope/sofa,FabienPean/sofa,Anatoscope/sofa,Anatoscope/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,hdeling/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa