Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/POCO/Foundation/include/Poco/SHA2Engine.h

@@ -0,0 +1,72 @@
+//
+// SHA2Engine.h
+//
+// Library: Foundation
+// Package: Crypt
+// Module:  SHA2Engine
+//
+// Definition of class SHA2Engine.
+//
+// Secure Hash Standard SHA-2 algorithm
+// (FIPS 180-4, see http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf)
+//
+// Based on the implementation of mbed TLS (Apache 2.0)
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Copyright (c) 2017, Applied Informatics Software Engineering GmbH
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_SHA2Engine_INCLUDED
+#define Foundation_SHA2Engine_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include "Poco/DigestEngine.h"
+
+
+namespace Poco {
+
+
+class Foundation_API SHA2Engine: public DigestEngine
+	/// This class implements the SHA-2 message digest algorithm.
+	/// (FIPS 180-4, see http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf)
+{
+public:
+	enum ALGORITHM
+	{
+		SHA_224 = 224,
+		SHA_256 = 256,
+		SHA_384 = 384,
+		SHA_512 = 512
+	};
+
+	SHA2Engine(ALGORITHM algorithm = SHA_256);
+	~SHA2Engine();
+
+	std::size_t digestLength() const;
+	void reset();
+	const DigestEngine::Digest& digest();
+
+protected:
+	void updateImpl(const void* data, std::size_t length);
+
+private:
+	void transform();
+
+	void* _context;
+	ALGORITHM _algorithm;
+	DigestEngine::Digest _digest;
+
+	SHA2Engine(const SHA2Engine&);
+	SHA2Engine& operator = (const SHA2Engine&);
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_SHA2Engine_INCLUDED