WiiUtils: Add function to get current system menu version

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/WiiUtils.java

@@ -29,4 +29,6 @@ public final class WiiUtils
   public static native int doOnlineUpdate(String region, WiiUpdateCallback callback);
 
   public static native boolean isSystemMenuInstalled();
+
+  public static native String getSystemMenuVersion();
 }