Fix race condition that could cause crash on exit

macosx/Snes9x/AppDelegate.m

@@ -238,6 +238,7 @@ static NSString * const kKeyboardPrefs = @"KeyboardConfig";
 
 - (IBAction)terminate:(id)sender
 {
+    [self.s9xEngine stop];
     [NSApp terminate:sender];
 }
 

macosx/mac-os.mm

@@ -3013,7 +3013,7 @@ void QuitWithFatalError ( NSString *message)
 
 - (void)stop
 {
-    pauseEmulation = true;
+    S9xExit();
 }
 
 - (BOOL)isRunning