Bug#1000660: TKIVtk library missing

[Roland Mas]

Hi all,

I happen to be working on packaging OCP and CadQuery too, so I stumbled 
on this very same problem (TKIVtk missing from the opencascade 
packages). I prepared an MR 
(https://salsa.debian.org/science-team/opencascade/-/merge_requests/5) 
that implements the separation of that part of opencascade into its own 
library+dev packages. It's part a revert of c688fcc7c, part an update to 
current code and vtk version, and part a splitting of ivtk into its own 
separate packages.

I'd appreciate a review and, if acceptable, a merge; I can live with the 
upload not happening right away, since I'm not yet ready with the rest 
of OCP/CadQuery, but an upload to experimental would be nice too.

Roland.