Detect OS X better.

Change-Id: Iebdb477a3763c4958ea34e9ccdafcbafbc5ddff8
Reviewed-on: http://gerrit.dmdirc.com/3068
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager

src/com/dmdirc/addons/ui_swing/Apple.java

@@ -168,7 +168,7 @@ public class Apple implements InvocationHandler {
      * @return true if we are running on OS X
      */
     public static boolean isApple() {
-        return (System.getProperty("mrj.version") != null);
+        return System.getProperty("os.name").contains("OS X");
     }
 
     /**