Fix all clang -Wstrict-prototypes warnings
Clang is considering making the -Wstrict-prototypes warning an error by default, see: https://discourse.llvm.org/t/rfc-enabling-wstrict-prototypes-by-default-in-c/60521
vtk has several such warnings, but they are all from third party libs.
I have fixed most upstream:
https://github.com/CGNS/CGNS/pull/332
https://github.com/Unidata/netcdf-c/pull/2239
https://gitlab.onelab.info/seanm/gl2ps/-/merge_requests/1
and created a ticket for another:
https://github.com/gsjaardema/seacas/issues/290
VTK just needs to update its copy of these third party libs...