cleanup + add constructor to FuncSpaceData


git-svn-id: https://geuz.org/svn/gmsh/trunk@19666 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@19667 59c8cabf-10d6-4a28-b43f-3936b85956c4
avoid to create PView if there are no data


git-svn-id: https://geuz.org/svn/gmsh/trunk@19668 59c8cabf-10d6-4a28-b43f-3936b85956c4
Fixed compilation of Python interface

git-svn-id: https://geuz.org/svn/gmsh/trunk@19669 59c8cabf-10d6-4a28-b43f-3936b85956c4