Bug#743177: libvtk6 should conflicts with libvtk5.8

[Mathieu Malaterre]

Package: libvtk6

Clearly there is something missing here. libvtk6 can be co-installed
with libvtk5.8. VTK API (ABI too) is completely incompatible in
between those two versions.

Typical scenarios that should not happen is an app linked against
vtkCommon and vtkCommonCore. This gets even worst with python

$ python
import vtkCommon
import vtkCommonCore

I guess the same is true for java + tcl binding.

So IMHO libvtk5.8 and libvtk6 should conflicts.