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/Encodings/samples/TextConverter/src/TextConverter.cpp

@@ -0,0 +1,51 @@
+//
+// TextConverter.cpp
+//
+// This sample demonstrates the text encodings support in POCO.
+//
+// Copyright (c) 2018, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#include "Poco/StreamConverter.h"
+#include "Poco/StreamCopier.h"
+#include "Poco/TextEncoding.h"
+#include "Poco/Encodings.h"
+#include <iostream>
+
+
+inline int usage()
+{
+	std::cout << "Usage: TextConverter <inEncoding> <outEncoding>" << std::endl;
+	return 1;
+}
+
+
+int main(int argc, char** argv)
+{
+	if (argc < 3) return usage();
+
+	try
+	{
+		Poco::registerExtraEncodings(); // register encodings from the PocoEncodings library
+
+		std::string inEncodingName(argv[1]);
+		std::string outEncodingName(argv[2]);
+
+		Poco::TextEncoding& inEncoding = Poco::TextEncoding::byName(inEncodingName);
+		Poco::TextEncoding& outEncoding = Poco::TextEncoding::byName(outEncodingName);
+
+		Poco::OutputStreamConverter conv(std::cout, inEncoding, outEncoding);
+		Poco::StreamCopier::copyStream(std::cin, conv);
+	}
+	catch (Poco::Exception& exc)
+	{
+		std::cerr << exc.displayText() << std::endl;
+		return 2;
+	}
+
+	return 0;
+}