Handle SIGINT (CTL+C) by gracefully shutting down

smocore/include/componentThread.h

@@ -110,6 +110,8 @@ public:
 
 	// Intentionally doesn't take a callback.
 	void exceptionInd(ComponentThread& thread);
+	// Intentionally doesn't take a callback.
+	void userShutdownInd();
 
 public:
 	ThreadId id;

smocore/include/marionette/marionette.h

@@ -13,6 +13,8 @@ class Marionette
 {
 };
 
+void exitMarionetteLoop();
+
 } // namespace mrntt
 
 struct CrtCommandLineArgs