Checklist:
- Write changelog
- Build and test windows installer
- Build tar.gz
- VER_TAG=r6.1; git archive --format=tar --prefix=xtalopt-$VER_TAG/ $VER_TAG | gzip > /tmp/xtalopt-$VER_TAG.tar.gz
- Tag stable branch with release version
- Upload windows installer
- Upload tarball
- Update blog
- Update wiki main page
- Update wiki Windows page
- Announce on mailing list
- Send in NVA to CPC (if needed)
