MaxOSX: settings fixes (#2371)

- Launch-At-Startup implementation for mac
- Remove "Window" tab in settings

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>

src/qt/bitcoin.cpp

@@ -211,9 +211,12 @@ int main(int argc, char *argv[])
 
     try
     {
+#ifndef Q_OS_MAC
         // Regenerate startup link, to fix links to old versions
+        // OSX: makes no sense on mac and might also scan/mount external (and sleeping) volumes (can take up some secs)
         if (GUIUtil::GetStartOnSystemStartup())
             GUIUtil::SetStartOnSystemStartup(true);
+#endif
 
         boost::thread_group threadGroup;