A class for types that can be converted to a hash value
Description
This package defines a class, 'Hashable', for types that can be converted to a
hash value. This class exists for the benefit of hashing-based data structures.
The package provides instances for basic types and a way to combine hash
values.
The 'Hashable' 'hash' values are not guaranteed to be stable across library
versions, operating systems or architectures. For stable hashing use named
hashes: SHA256, CRC32 etc.
