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/NetSSL_OpenSSL/include/Poco/Net/FTPSClientSession.h

@@ -0,0 +1,101 @@
+//
+// FTPSClientSession.h
+//
+// Library: NetSSL_OpenSSL
+// Package: FTPS
+// Module:  FTPSClientSession
+//
+// Definition of the FTPSClientSession class.
+//
+// Copyright (c) 2005-2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef NetSSL_FTPSClientSession_INCLUDED
+#define NetSSL_FTPSClientSession_INCLUDED
+
+
+#include "Poco/Net/NetSSL.h"
+#include "Poco/Net/Context.h"
+#include "Poco/Net/FTPClientSession.h"
+
+
+namespace Poco {
+namespace Net {
+
+
+class NetSSL_API FTPSClientSession: public Poco::Net::FTPClientSession
+	/// This is an extension of FTPClientSession that supports
+	/// FTP over SSL/TLS using the AUTH SSL/AUTH TLS and PBSZ/PROT
+	/// commands according to RFC 4217.
+{
+public:
+	FTPSClientSession();
+		/// Creates an FTPSClientSession.
+		///
+		/// Passive mode will be used for data transfers.
+
+	explicit FTPSClientSession(Context::Ptr pContext);
+		/// Creates an FTPSClientSession using the given Context.
+		///
+		/// Passive mode will be used for data transfers.
+
+	FTPSClientSession(const StreamSocket& socket, bool readWelcomeMessage = true, bool enableFTPS = true, Context::Ptr pContext = nullptr);
+		/// Creates an FTPSClientSession using the given
+		/// connected socket for the control connection.
+		///
+		/// Passive mode will be used for data transfers.
+
+	FTPSClientSession(const std::string& host, Poco::UInt16 port = FTP_PORT, const std::string& username = "", const std::string& password = "", Context::Ptr pContext = nullptr);
+		/// Creates an FTPSClientSession using a socket connected
+		/// to the given host and port. If username is supplied,
+		/// login is attempted.
+		///
+		/// Passive mode will be used for data transfers.
+
+	virtual ~FTPSClientSession();
+
+	void enableFTPS(bool enable = true);
+		/// Enable or disable FTPS (FTP over SSL/TLS).
+
+	bool isSecure() const;
+		/// Returns true if the session is FTPS.
+
+protected:
+	virtual StreamSocket establishDataConnection(const std::string& command, const std::string& arg);
+		/// Create secure data connection
+
+	virtual void receiveServerReadyReply();
+		/// Function that read server welcome message after connetion and set and make secure socket
+
+private:
+	void beforeCreateDataSocket();
+		///Send commands to check if we can encrypt data socket
+
+	void afterCreateControlSocket();
+		///Send commands to make SSL negotiating of control channel
+
+	bool _enableFTPS = true;
+	bool _secureDataConnection = false;
+	Context::Ptr _pContext;
+};
+
+
+//
+// inlines
+//
+inline bool FTPSClientSession::isSecure() const
+{
+	if (_pControlSocket != nullptr)
+		return _pControlSocket->secure();
+	return false;
+}
+
+
+} } // namespace Poco::Net
+
+
+#endif // #define NetSSL_FTPSClientSession_INCLUDED