* [tests] Determine at runtime instead of compile time whether LinkAll is enabled. Fixes#3812.
This way we can remove the LINKALL define, which also means nobody can forget
to define it when building using LinkAll.
https://github.com/xamarin/xamarin-macios/issues/3812
The [Protocol] attributes the test checks for are not linked away in
monotouch-test (because monotouch-test only links SDK assemblies), but they
are linked away in link all, so adjust the test accordingly.
* [tests] Remove Classic SDK tests.
* Remove XI/Classic support.
This also means we can remove support for the legacy registrars.
* [monotouch-test] Remove legacy registrar tests.
* [tests/mtouch] Remove Classic tests (and legacy registrar logic).
* [tests/scripted] Fix tests to reference Xamarin.iOS.dll.
Rolf Bjarne Kvinge