This is a new pure Rust implementation of the Equi-X algorithm
designed by tevador for Tor's onion service proof of work puzzle v1.
Equi-X is an asymmetric puzzle algorithm based on Equihash, with
N=60, K=3, the XOR replaced with modular addition, a 16-bit index
space, and HashX as the inner hash function.
Signed-off-by: Micah Elizabeth Scott <beth@torproject.org>