Kmax

Kmax now extracts top-level architecture-specific directories.
Previously, all top-level directories were assumed to be always
included, but some architcture-specific directories, e.g., with
core-y, are configurable. So this version also collects
subdirectories from these other Kbuild variables and adds them to the
Kmax formulas.

Add the klocalizer tool for creating a configuration for a given compilation unit. This version merges kmax, kclause, and klocalizer into a single installable project. The version has a number of improvements to the formulas generated by kmax and kclause and adds support for multiple architectures to klocalizer.

This version adds back in BDD support, dramatically improving performance. Linux 5.3.11 takes 6 minutes instead of 4 hours. Z3 is still used, because it is faster to write out the resulting formulas, since it avoids exhaustive enumeration of the solutions.

This version removes the dependency of pycudd, relying entirely on z3.

This version of Kmax converts the repository into a stand-alone python project. Removed are the Kconfig analyses and experiments, which can be found in older versions of Kmax.

This version of Kmax includes several new features and improvements:

- Integration with [z3](https://rise4fun.com/z3) instead of BDDs. This enables Kmax to more efficiently work with Boolean expressions and use better simplification tactics. Special thanks to [ThanhVu Nguyen](https://cse.unl.edu/~tnguyen/) for helping integrate z3 into Kmax.
- A new tool called Kclause, which translates Kconfig specifications to Boolean expressions. This has both BDD and z3 backends. Special thanks to [Jeho Oh](https://www.linkedin.com/in/jeho-oh-110a2092) for spending time to work on Kconfig's semantics.
- There are many more test cases for both Kmax and Kclause in `tests/`
- Documentation is somewhat improved in README.md to make it easier to run Kmax on the whole Linux kernel.