Fix edge case where lazy default properties can return the wrong value on first access if the initializer is naughty and overwrites the default manually. (Fixes issue #234)
Stop generating 'x + y' for string addition since the semantics don't match C#. Fixes issue #239.
Fix JSIL.ConcatString's behavior for nulls.
Checkpoint some work on issue #243:
Assign closure variables better, scope-unique names.
Implement some more LINQ methods (SelectMany, Empty)
Make JSIL.Dispose work on null.