BUG: Add VTK_VERSION for older VTK versions

For older VTK's, VTK_VERSION is not defined. It needs to be setup manually.

See ITK-3304

Change-Id: I5efec656190e7417c7a2cbfa1b27b8b545261ca0
Merge topic 'VTKVersion'

f5b64b1e BUG: Add VTK_VERSION for older VTK versions