Upgraded vtktiff from 3.8.2 to 4.0.6 which is latest upstream release
- Uses update.sh approach to subtree merge from upstream clone at https://gitlab.kitware.com/third-party/tiff
- Most significant benefit is bigtiff support which supports files larger than 4gb
- Latest release notes are at http://www.remotesensing.org/libtiff/v4.0.6.html