hg: lambda/lambda/langtools: DA/DU, effectively-final cleanup

[Brian Goetz]

>> DA/DU, effectively-final cleanup
>> *) remove support for lambda recursion through local variable
> 
> What was the rationale for that? Does it complicate runtime lambda 
> construction/(de)serailization too much for the limited usability it provides?

Exactly right.  The support for recursion through DA/DU was limited (had to put the identifier for the lambda outside the scope of the lambda; not strong enough to support mutually recursive lambdas) and at the same time, complicated the runtime translation (which in turn complicated VM optimization.)  So, it was not carrying its weight.