Reintroducing the logging::Manager's Terminate() method.

It doesn't do anything else than simply forwarding to FlushBuffers().

This is just for consistency in terminate_bro() where components get
their Terminate() called so that the main code doesn't need to know
anything more specific about what particular action to take at
shutdown.

src/logging/Manager.h

@@ -155,6 +155,11 @@ public:
 	 */
 	void FlushBuffers();
 
+	/**
+	 * Signals the manager to shutdown at Bro's termination.
+	 */
+	void Terminate();
+
 	/**
 	 * Returns a list of supported output formats.
 	 */