Replace deprecated Mac OS specific property

When executing the launch script under Mac OS X 10.9 there is a
deprecation warning:

~~~
com.apple.macos.useScreenMenuBar has been deprecated. Please switch to
apple.laf.useScreenMenuBar
~~~

The change reflects the current Apple Java developer guide [here](https://developer.apple.com/library/mac/documentation/java/Reference/Java_PropertiesRef/Articles/JavaSystemProperties.html).