v0.3.10: frozen codebase + next steps

After the broken 0.3.9, I decided to revert the faulty PR #105, reopening the issues #90 and #103. Also, this release includes all the other pending bugs. As it is getting harder to modify the codebase, I decided to freeze it. I'm going to merge only PRs fixing bugs with proper tests.

On the other hand, I will start a new cleanroom implementation. Existing tests will be reviewed and used as "test subjects". Also, I plan to collect real-world examples to use them also as "test subjects" in a separate repository.

In this process, I would like to work from the bottom to the top, focusing on getting the core right. I plan to keep a legacy compatibility layer, but the new API may differ from the current one to allow better maintenance and new features.