FastSha256Core: Simplified a constant expression.
FastSha256Core: De-optimized computation method for better compatibility with default JVM options, tweaked superclass field visibility.
FastSha256Core: Optimized speed by partially unrolling the computation.
FastSha512Core, Sha512Core, Sha: Optimized speed by partially unrolling the computation (differently from FastSha256Core), modified Sha512Core to be suitable as a superclass, made the fast SHA-512 hasher the default implementation.