Use a single point where the different enpoints can be found so that
if they need to be updated (server issues or other) it is a simple
change that will affect all tests in monotouch-tests
* Fix many version checks to be based on Xcode version instead of iOS version.
* Added/fixed a few expected values according to platform version to match behavior in older macOS versions.
https://bugzilla.xamarin.com/show_bug.cgi?id=37175
NSUrlSession's Create*Task methods may return an object of the wrong
type (NSUrlSessionTask instead of NSUrl[Data|Download|Upload]SessionTask),
so we need to bypass our type check when creating the managed object,
otherwise we end up throwing InvalidCastExceptions randomly. We will
return the type that is declared on the headers so if the native side
returns a cat and headers says it barks we'll we make it bark :).
Rolf Bjarne Kvinge
Manuel de la Pena
Timothy Risi
Alex Soto