Migrate off travis-ci.org for CI builds/testing

[gvansickle]

[gvansickle]

Some info on options and advice on how to "Don’t Let This Happen Again" here:
https://earthly.dev/blog/migrating-from-travis/

[gvansickle]

Will try out Github Actions. See e.g.:
https://docs.github.com/en/actions/migrating-to-github-actions/migrating-from-travis-ci-to-github-actions

[gvansickle]

Putting this work on hold for now. GitHub runners have std lib version 11 atm, currently need version 12.

[gvansickle]

Now have this working by using Podman to run a Fedora instance (see https://fedoramagazine.org/github-actions-use-podman-to-run-fedora-linux/ for the idea). Not complete, but enough to do a "make check" (skipping the corpus-requiring tests).