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/DataURIStream.h

@@ -0,0 +1,78 @@
+//
+// DataURIStream.h
+//
+// Library: Foundation
+// Package: Streams
+// Module:  DataURIStreamFactory
+//
+// Definition of the DataURIStream class.
+//
+// Copyright (c) 2019, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_DataURIStream_INCLUDED
+#define Foundation_DataURIStream_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include <istream>
+#include <memory>
+
+
+namespace Poco {
+
+
+class Base64Decoder;
+class MemoryInputStream;
+class URI;
+
+
+class Foundation_API DataURIStreamIOS: public virtual std::ios
+	/// The base class for DataURIStream.
+	///
+	/// This class is needed to ensure the correct initialization
+	/// order of the stream buffer and base classes.
+{
+public:
+	DataURIStreamIOS(const URI& uri);
+	~DataURIStreamIOS();
+	std::streambuf* rdbuf();
+
+protected:
+	std::streambuf* _buf;
+
+private:
+	DataURIStreamIOS(const DataURIStreamIOS&);
+	DataURIStreamIOS& operator = (const DataURIStreamIOS&);
+	std::string _data;
+	std::unique_ptr<MemoryInputStream> _memoryStream;
+	std::unique_ptr<Base64Decoder> _base64Decoder;
+};
+
+
+class Foundation_API DataURIStream: public DataURIStreamIOS, public std::istream
+	/// An input stream for reading data from a data URI.
+	/// For example, when constructed from  "data:text/plain;base64,SGVsbG8sIFdvcmxkIQ%3D%3D" it reads "Hello, World!".
+{
+public:
+	DataURIStream(const URI& uri);
+		/// Creates a DataURIStream for the given data URI,
+		/// ready for reading data.
+		/// Throws a DataFormatException exception if the data is incorrect format.
+	~DataURIStream();
+		/// Destroys the DataURIStream.
+
+private:
+	DataURIStream(const DataURIStream&);
+	DataURIStream& operator = (const DataURIStream&);
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_DataURIStream_INCLUDED