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/Base64Encoder.h

@@ -0,0 +1,140 @@
+//
+// Base64Encoder.h
+//
+// Library: Foundation
+// Package: Streams
+// Module:  Base64
+//
+// Definition of class Base64Encoder.
+//
+// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_Base64Encoder_INCLUDED
+#define Foundation_Base64Encoder_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include "Poco/UnbufferedStreamBuf.h"
+#include <ostream>
+
+
+namespace Poco {
+
+
+enum Base64EncodingOptions
+{
+	BASE64_URL_ENCODING = 0x01,
+		/// Use the URL and filename-safe alphabet,
+		/// replacing '+' with '-' and '/' with '_'.
+		///
+		/// Will also set line length to unlimited.
+
+	BASE64_NO_PADDING   = 0x02
+		/// Do not append padding characters ('=') at end.
+};
+
+
+class Foundation_API Base64EncoderBuf: public UnbufferedStreamBuf
+	/// This streambuf base64-encodes all data written
+	/// to it and forwards it to a connected
+	/// ostream.
+	///
+	/// Note: The characters are directly written
+	/// to the ostream's streambuf, thus bypassing
+	/// the ostream. The ostream's state is therefore
+	/// not updated to match the buffer's state.
+{
+public:
+	Base64EncoderBuf(std::ostream& ostr, int options = 0);
+	~Base64EncoderBuf();
+
+	int close();
+		/// Closes the stream buffer.
+
+	void setLineLength(int lineLength);
+		/// Specify the line length.
+		///
+		/// After the given number of characters have been written, 
+		/// a newline character will be written.
+		///
+		/// Specify 0 for an unlimited line length.
+
+	int getLineLength() const;
+		/// Returns the currently set line length.
+
+private:
+	int writeToDevice(char c);
+
+	int             _options;
+	unsigned char   _group[3];
+	int             _groupLength;
+	int             _pos;
+	int             _lineLength;
+	std::streambuf& _buf;
+	const unsigned char* _pOutEncoding;
+
+	static const unsigned char OUT_ENCODING[64];
+	static const unsigned char OUT_ENCODING_URL[64];
+
+	friend class Base64DecoderBuf;
+
+	Base64EncoderBuf(const Base64EncoderBuf&);
+	Base64EncoderBuf& operator = (const Base64EncoderBuf&);
+};
+
+
+class Foundation_API Base64EncoderIOS: public virtual std::ios
+	/// The base class for Base64Encoder.
+	///
+	/// This class is needed to ensure the correct initialization
+	/// order of the stream buffer and base classes.
+{
+public:
+	Base64EncoderIOS(std::ostream& ostr, int options = 0);
+	~Base64EncoderIOS();
+	int close();
+	Base64EncoderBuf* rdbuf();
+
+protected:
+	Base64EncoderBuf _buf;
+
+private:
+	Base64EncoderIOS(const Base64EncoderIOS&);
+	Base64EncoderIOS& operator = (const Base64EncoderIOS&);
+};
+
+
+class Foundation_API Base64Encoder: public Base64EncoderIOS, public std::ostream
+	/// This ostream base64-encodes all data
+	/// written to it and forwards it to
+	/// a connected ostream.
+	/// Always call close() when done
+	/// writing data, to ensure proper
+	/// completion of the encoding operation.
+	///
+	/// The class implements RFC 4648 - https://tools.ietf.org/html/rfc4648
+	///
+	/// Note: The characters are directly written
+	/// to the ostream's streambuf, thus bypassing
+	/// the ostream. The ostream's state is therefore
+	/// not updated to match the buffer's state.
+{
+public:
+	Base64Encoder(std::ostream& ostr, int options = 0);
+	~Base64Encoder();
+
+private:
+	Base64Encoder(const Base64Encoder&);
+	Base64Encoder& operator = (const Base64Encoder&);
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_Base64Encoder_INCLUDED