Add version header for CmdStan

[andrjohns]

Submisison Checklist

• Run tests: ./runCmdStanTests.py src/test
• Declare copyright holder and open-source license: see below

Summary:

This PR adds a version.hpp header following the conventions of the Stan and Math libraries

Intended Effect:

The CmdStan version is currently only recorded in the Makefile, which means that any downstream users need to also include the makefiles in order to identify the version of the CmdStan headers & sources.

This allows downstream users to identify the version of the CmdStan headers/sources without needing to include & parse the makefile, improves consistency with the Stan & Math libraries

How to Verify:

Side Effects:

Documentation:

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company): Andrew Johnson

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[WardBrian]

Seems useful. Thoughts on having this be the version we put in the CSV files? Code is here:
https://github.com/stan-dev/cmdstan/blob/develop/src/cmdstan/write_stan.hpp

[WardBrian]

Also tagging @serban-nicusor-toptal so he would know that there is a new file that needs updating each release!

[rok-cesnovar]

Seems useful. Thoughts on having this be the version we put in the CSV files?

I don't see a case where the cmdstan and stan versions would diverge, but it depends on what we want to write in the file, the Stan version of the interface version. I think the Stan version?

[WardBrian]

I don't see a case where the cmdstan and stan versions would diverge

They've diverged right now (CmdStan is on 2.33.1, Stan on 2.33.0) because the latest bugfix release didn't require any changes to Stan or Math

[rok-cesnovar]

Oh right. I don't really have a preference honestly, was just being nitpicky :)

[WardBrian]

I think given a cmdstan version, there is always a unique version of Stan shipped with that (we never update Stan without updating CmdStan) but the inverse need not be true (e.g., right now), so it seems reasonable to include the cmdstan version in the csv. It's not a big deal either way, I think