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/ValidArgs.h

@@ -0,0 +1,74 @@
+//
+// ValidArgs.h
+//
+// Library: Foundation
+// Package: Cache
+// Module:  ValidArgs
+//
+// Definition of the ValidArgs class.
+//
+// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_ValidArgs_INCLUDED
+#define Foundation_ValidArgs_INCLUDED
+
+
+#include "Poco/Foundation.h"
+
+
+namespace Poco {
+
+
+template <class TKey>
+class ValidArgs
+{
+public:
+	ValidArgs(const TKey& key):
+		_key(key), 
+		_isValid(true)
+	{
+	}
+
+	ValidArgs(const ValidArgs& args): 
+		_key(args._key), 
+		_isValid(args._isValid)
+	{
+	}
+
+	~ValidArgs()
+	{
+	}
+	
+	const TKey&	key() const
+	{
+		return _key;
+	}
+
+	bool isValid() const
+	{
+		return _isValid;
+	}
+
+	void invalidate()
+	{
+		_isValid = false;
+	}
+
+protected:
+	const TKey& _key;
+	bool        _isValid;
+
+private:
+	ValidArgs& operator = (const ValidArgs& args);
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_ValidArgs_INCLUDED