Version 2015 R4.1: Fixed platform check on Xamarin mobile platforms

This release fixes an issue with platform check routine in 2015 R4 that stopped working correctly with the latest Xamarin Studio update. Due to this issue, Xamarin.Android was detected as Xamarin.iOS, causing a failure.

If you are not targeting Xamarin.Android or Xamarin.iOS, you don't have to upgrade - the platform check routine is the only functionality change in 2015 R4.1.