Add compile-fail tests

[rylev]

Using a tool lime TryBuild we can test that certain code does not build and that the diagnostics the end user gets are what we expect.

[zachlute]

If this happens, it would be great to have a test that trying to move things between threads doesn't compile for types that aren't MarshalType.Agile.

[kennykerr]

This is not something I'm likely to get to.