Move externals to third_party and package licenses

[JeodC]

Pull Request Type

• [ ] GitHub Workflow changes
• [ ] Documentation or Wiki changes
• [x] Build and Dependency changes
• [ ] Runtime changes
  • [ ] Render changes
  • [ ] Audio changes
  • [ ] Input changes
  • [ ] Network changes
  • [ ] Other changes

Description

This pull piggybacks on #301 and consolidates.

• External dependencies moved to third_party directory
• ${subdir}_LICENSE.txt files created for each external dependency inside third_party
• License files are added to Descent3/licenses/ at build time
• CMakeLists.txt includes third_party headers under include_directories

Checklist

• [x] I have tested my changes locally and verified that they work as intended.
• [x] I have documented any new or modified functionality.
• [x] I have reviewed the changes to ensure they do not introduce any unnecessary complexity or duplicate code.
• [x] I understand that by submitting this pull request, I am agreeing to license my contributions under the project's license.

[winterheart]

Isn't MD5 implementation is our now? We don't have to make it as third_party. As it have same license and same copyright owners, it will be integral part of project.

[JeodC]

Isn't MD5 implementation is our now? We don't have to make it as third_party. As it have same license and same copyright owners, it will be integral part of project.

Except from a Discord conversation with its author:

Jeod — 05/20/2024 9:03 AM
@Parabolicus What did you license md5 under again?
Parabolicus — 05/20/2024 9:05 AM
it is my original code so whatever license works
Jeod — 05/20/2024 9:06 AM
I was going to put it in the third_party dir, unless you'd say it isn't really an external dependency.
Up to you.
@Parabolicus Do you mind briefly checking out 375 and let me know if you want any changes to the md5 license?
I kept it third party so others could feel more inclined to copy and use it for their own projects (not tying it to Descent 3 explicitly).
Parabolicus — 05/20/2024 9:58 AM
no objections

[JeodC]

MD5 is not a third-party, it has no upstream, we maintain it, and it was written explicitly for this project

No we do not maintain it. We certainly can, but ultimately a non-organization member wrote it. You're welcome to get further clarification from @ziplantil.

[Lgt2x]

MD5 is not a third-party, it has no upstream, we maintain it, and it was written explicitly for this project

No we do not maintain it. We certainly can, but ultimately a non-organization member wrote it. You're welcome to get further clarification from @ziplantil.

A 3rd party has an UPSTREAM repository where we can pull changes from. This is not the case here, because it was written for this project, hence not a 3rd party.