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/NotificationCenter.h

@@ -0,0 +1,139 @@
+//
+// NotificationCenter.h
+//
+// Library: Foundation
+// Package: Notifications
+// Module:  NotificationCenter
+//
+// Definition of the NotificationCenter class.
+//
+// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_NotificationCenter_INCLUDED
+#define Foundation_NotificationCenter_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include "Poco/Notification.h"
+#include "Poco/Mutex.h"
+#include "Poco/SharedPtr.h"
+#include <vector>
+#include <cstddef>
+
+
+namespace Poco {
+
+
+class AbstractObserver;
+
+
+class Foundation_API NotificationCenter
+	/// A NotificationCenter is essentially a notification dispatcher. 
+	/// It notifies all observers of notifications meeting specific criteria.
+	/// This information is encapsulated in Notification objects.
+	/// Client objects register themselves with the notification center as observers of 
+	/// specific notifications posted by other objects. When an event occurs, an object 
+	/// posts an appropriate notification to the notification center. The notification  
+	/// center invokes the registered method on each matching observer, passing the notification 
+	/// as argument.
+	///
+	/// The order in which observers receive notifications is undefined. 
+	/// It is possible for the posting object and the observing object to be the same.
+	/// The NotificationCenter delivers notifications to observers synchronously. 
+	/// In other words the postNotification() method does not return until all observers have 
+	/// received and processed the notification. 
+	/// If an observer throws an exception while handling a notification, the NotificationCenter
+	/// stops dispatching the notification and postNotification() rethrows the exception.
+	///
+	/// In a multithreaded scenario, notifications are always delivered in the thread in which the 
+	/// notification was posted, which may not be the same thread in which an observer registered itself.
+	///
+	/// The NotificationCenter class is basically a C++ implementation of the NSNotificationCenter class
+	/// found in Apple's Cocoa (or OpenStep).
+	///
+	/// While handling a notification, an observer can unregister itself from the notification center,
+	/// or it can register or unregister other observers. Observers added during a dispatch cycle
+	/// will not receive the current notification.
+	///
+	/// The method receiving the notification must be implemented as
+	///     void handleNotification(MyNotification* pNf);
+	/// The handler method gets co-ownership of the Notification object
+	/// and must release it when done. This is best done with an AutoPtr:
+	///     void MyClass::handleNotification(MyNotification* pNf)
+	///     {
+	///         AutoPtr<MyNotification> nf(pNf);
+	///         ...
+	///     }
+	///
+	/// Alternatively, the NObserver class template can be used to register a callback
+	/// method. In this case, the callback method receives the Notification in an
+	/// AutoPtr and thus does not have to deal with object ownership issues:
+	///     void MyClass::handleNotification(const AutoPtr<MyNotification>& pNf)
+	///     {
+	///         ...
+	///     }
+{
+public:
+	NotificationCenter();
+		/// Creates the NotificationCenter.
+
+	~NotificationCenter();
+		/// Destroys the NotificationCenter.
+
+	void addObserver(const AbstractObserver& observer);
+		/// Registers an observer with the NotificationCenter.
+		/// Usage:
+		///     Observer<MyClass, MyNotification> obs(*this, &MyClass::handleNotification);
+		///     notificationCenter.addObserver(obs);
+		///
+		/// Alternatively, the NObserver template class can be used instead of Observer.
+
+	void removeObserver(const AbstractObserver& observer);
+		/// Unregisters an observer with the NotificationCenter.
+
+	bool hasObserver(const AbstractObserver& observer) const;
+		/// Returns true if the observer is registered with this NotificationCenter.
+
+	void postNotification(Notification::Ptr pNotification);
+		/// Posts a notification to the NotificationCenter.
+		/// The NotificationCenter then delivers the notification
+		/// to all interested observers.
+		/// If an observer throws an exception, dispatching terminates
+		/// and the exception is rethrown to the caller.
+		/// Ownership of the notification object is claimed and the
+		/// notification is released before returning. Therefore,
+		/// a call like
+		///    notificationCenter.postNotification(new MyNotification);
+		/// does not result in a memory leak.
+
+	bool hasObservers() const;
+		/// Returns true iff there is at least one registered observer.
+		///
+		/// Can be used to improve performance if an expensive notification
+		/// shall only be created and posted if there are any observers.
+		
+	std::size_t countObservers() const;
+		/// Returns the number of registered observers.
+		
+	static NotificationCenter& defaultCenter();
+		/// Returns a reference to the default
+		/// NotificationCenter.
+
+private:
+	typedef SharedPtr<AbstractObserver> AbstractObserverPtr;
+	typedef std::vector<AbstractObserverPtr> ObserverList;
+
+	ObserverList  _observers;
+	mutable Mutex _mutex;
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_NotificationCenter_INCLUDED