[c, cpp]: support VERSION file for CMake ABI versioning

[chybz]

🤔 What's changed?

• [c] slight update to existing CMakeFiles.txt to propagate VERSION. Closes: Please version the ABI for C shared libraries #320
• [cpp] add generic support for ABI versioning with VERSION

⚡️ What's your motivation?

make sure ABI is versioned for shared libraries

🏷️ What kind of change is this?

• ⚡ New feature (non-breaking change which adds new behaviour)
• 💥 Breaking change (incompatible changes to the API)

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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[mpkorstanje]

Is this not a breaking change?

[mpkorstanje]

Please also update the CHANGELOG.md so things are properly documented on release.

[chybz]

@mpkorstanje I'm going to merge. Can you please activate the VERSION automatic update for gherkin/cpp and messages/cpp ?

[mpkorstanje]

It's already merged. cucumber/polyglot-release#104

Question though, is the change in namespace that you included breaking in a Semver context? Doesn't matter for merging but does matter when it comes to deciding the next version number.

[chybz]

TLDR: yes. Sincerely hope that's not overly problematic.

It is from a pure compilation standpoint, but function signatures are exactly the same as before, so this should be a minimal hassle for the (no more than 2 people I think) current cpp user-base.

[mpkorstanje]

Okay cheers! I didn't see your edit until now.

[mpkorstanje]

And no problem! Version numbers are relatively cheap.