Chiavdf

Added

- Add form compression, use it in Python bindings and VDF client. Using compressed representation of quadratic forms reduces their serialized size from 130 to 100 bytes (for forms with 1024-bit discriminant). This shrinks the size of VDF outputs and VDF proofs. The form compression algorithm is based on ["Trustless Groups of Unknown Order with Hyperelliptic Curves"](https://eprint.iacr.org/2020/196) by Samuel Dobson, Steven D. Galbraith and Benjamin Smith.
- We now verify form size when deserializing.
- MacOS universal wheels to support MacOS ARM64 are built for Python 3.9.

Changed

- This is a breaking change from the 0.13.x series.

Added

- We now build both MacOS x86_64 and MacOS universal wheels.

Added

- Replace GMP's primality test function with our own based on Baillie-PSW. The new primality test is based on the 2020 paper ["Strengthening the Baillie-PSW primality test" by Robert Baillie, Andrew Fiori, Samuel S. Wagstaff Jr](https://arxiv.org/abs/2006.14425). The new test works approximately 20% faster than GMP library's mpz_probab_prime_p() function when generating random 1024-bit primes.

Changed

- Refactor form exponentiation, start from top bits of exponent. This slightly improves performance of VDF proof verification.

Fixed

- We've moved to pybind 2.6.2 to avoid a possible shutdown bug in Python 3.9.0.

Added

- Use only Baillie-PSW primality test when hashing to prime. This increases performance of hashing to prime when generating the
discriminant by about 2x.