enh(Foundation): modernised header files (override, using, nullptr, ...)

Foundation/include/Poco/Task.h

@@ -91,7 +91,7 @@ public:
 		/// Do whatever the task needs to do. Must
 		/// be overridden by subclasses.
 
-	void run();
+	void run() override;
 		/// If task has not been cancelled prior to this call, it
 		/// calls the task's runTask() method and notifies the owner of
 		/// the task's start and completion.
@@ -144,7 +144,7 @@ protected:
 	TaskState setState(TaskState state);
 		/// Sets the task's state.
 
-	virtual ~Task();
+	~Task() override;
 		/// Destroys the Task.
 
 private: