Fix to respect NONATIVEHASH in Crypto.Hashes.cs.
Fix to respect NONATIVEHASH in Crypto.Hashes.cs.

NONATIVEHASH was not respected everywhere, causing the project to fail unexpectedly in a target platform (Blazor wasm) where System.Security.Cryptography is not supported.

Added a missing overload for HMACSHA512, and some small fixes to restore the build.
MetacoSA/NBitcoin,MetacoSA/NBitcoin,NicolasDorier/NBitcoin