Code Review: Issues with Thread#kill and raising exception from ensure clause

tfpt review “/shelveset:kill;REDMOND\sborde”

Comment :
Added more tests for Thread#kill, and fixed bugs that were exposed.
Throwing an exception from the ensure clause exposes new code paths.

Ruby allows Thread#kill to be completely subverted (not just deferred
as an infinite loop in an ensure clause would do) by raising an
exception from a ensure clause. I have not matched that behavior, and
left it as a IronRuby bug for now.

Are any methods in RubyOps Exceptions #region (including those added by
this shelveset) emitted to IL? If not they should rather be in RubyUtils

On the other hand, SourceUnitTree.CheckForAsyncRaiseViaThreadAbortshould
should be marked as [Emitted], be in RubyOps.cs and
SourceUnitTree.GenerateCheckForAsyncException should use
Methods.CheckForAsyncRaiseViaThreadAbort to get the method.

Could we add a public helper that calls thread.Abort(new
ThreadExitMarker()); move the private ThreadExitMarker class and
IsRubyThreadExit to RubyUtils? Then we won’t need to duplicate the
marker class in ThreadOps?

Other than that, looks good.