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/TextConverter.h

@@ -0,0 +1,93 @@
+//
+// TextConverter.h
+//
+// Library: Foundation
+// Package: Text
+// Module:  TextConverter
+//
+// Definition of the TextConverter class.
+//
+// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_TextConverter_INCLUDED
+#define Foundation_TextConverter_INCLUDED
+
+
+#include "Poco/Foundation.h"
+
+
+namespace Poco {
+
+
+class TextEncoding;
+
+
+class Foundation_API TextConverter
+	/// A TextConverter converts strings from one encoding
+	/// into another.
+{
+public:
+	typedef int (*Transform)(int);
+		/// Transform function for convert.
+		
+	TextConverter(const TextEncoding& inEncoding, const TextEncoding& outEncoding, int defaultChar = '?');
+		/// Creates the TextConverter. The encoding objects must not be deleted while the
+		/// TextConverter is in use.
+
+	~TextConverter();
+		/// Destroys the TextConverter.
+		
+	int convert(const std::string& source, std::string& destination, Transform trans);
+		/// Converts the source string from inEncoding to outEncoding
+		/// and appends the result to destination. Every character is
+		/// passed to the transform function.
+		/// If a character cannot be represented in outEncoding, defaultChar
+		/// is used instead.
+		/// Returns the number of encoding errors (invalid byte sequences
+		/// in source).
+
+	int convert(const void* source, int length, std::string& destination, Transform trans);
+		/// Converts the source buffer from inEncoding to outEncoding
+		/// and appends the result to destination. Every character is
+		/// passed to the transform function.
+		/// If a character cannot be represented in outEncoding, defaultChar
+		/// is used instead.
+		/// Returns the number of encoding errors (invalid byte sequences
+		/// in source).
+
+	int convert(const std::string& source, std::string& destination);
+		/// Converts the source string from inEncoding to outEncoding
+		/// and appends the result to destination.
+		/// If a character cannot be represented in outEncoding, defaultChar
+		/// is used instead.
+		/// Returns the number of encoding errors (invalid byte sequences
+		/// in source).
+
+	int convert(const void* source, int length, std::string& destination);
+		/// Converts the source buffer from inEncoding to outEncoding
+		/// and appends the result to destination.
+		/// If a character cannot be represented in outEncoding, defaultChar
+		/// is used instead.
+		/// Returns the number of encoding errors (invalid byte sequences
+		/// in source).
+
+private:
+	TextConverter();
+	TextConverter(const TextConverter&);
+	TextConverter& operator = (const TextConverter&);
+
+	const TextEncoding& _inEncoding;
+	const TextEncoding& _outEncoding;
+	int                 _defaultChar;
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_TextConverter_INCLUDED