FIX: compilation with libc++ (on clang)

git-svn-id: svn://scm.gforge.inria.fr/svnroot/sofa/trunk@10705 b7f1a160-662a-0410-a6d8-bea165342f16
Fix MeshToImage was broken on rendering backfaces in the rasterizer from previous commit.

git-svn-id: svn://scm.gforge.inria.fr/svnroot/sofa/trunk@10706 b7f1a160-662a-0410-a6d8-bea165342f16
BarycentricMapping: cleaning mask test

git-svn-id: svn://scm.gforge.inria.fr/svnroot/sofa/trunk@10707 b7f1a160-662a-0410-a6d8-bea165342f16