Fix big endianess support in InternalMessageDigest and PBKDF2

- Replace sha1/md5 implementation by ones from https://github.com/nmaier/crypto
- Add endianess functionality fro https://github.com/nmaier/crypto

Closes GH-239
Drop WinMessageDigestImpl.

The algorithms the `CryptProv` on Windows supports does not currently
include SHA-224, so there is a "dark spot" in this implementation. Also
on Win XP < SP3, most of the SHA-2 family is not actually supported.
All other implementation provide support for MD5, SHA-1 and all of the
SHA-2 family, hence drop the incomplete WinMessageDigest implementation
in favor of any other supported implementation (at least the internal
implementation is always available at compile-time).