SEACAS is now using versions instead of just relying on always
installing master. There are now tagged versions.
The most recent version is the first that can be used with a
non-patched develop version of the CGNS package; previously, seacas
required that the CGNS library have some internally-developed patch
applied, but this is no longer needed.
Also, added support for adios2 package with the adios2 variant.
This currently defaults to off.
b8175e3fae