Bug in ReferenceSpace::getJacobian -- Has to take sign of determinant into account when flipping elements ! + FunctionSpaceVector::interpolateDerivative + Mapper::hDiv -- do not use fabs in mapping

git-svn-id: https://geuz.org/svn/gmsh/trunk@18212 59c8cabf-10d6-4a28-b43f-3936b85956c4