deduplicating lambda methods

[Brian Goetz]

> That number doesn't tell the whole story about whether deduplication 
> is useful
> in practice, but if nothing else it lets us measure the relative 
> improvement from
> changes to the deduplication logic.

One reason I encouraged this project is that it is synergistic with 
other optimizations in the pipeline, namely using ConstantDynamic 
(condy) to translate non-capturing lambdas and method refs.  This has a 
direct performance benefit (lighter than indy) and offers more sharing.  
Further, a little farther down the road is more aggresive constant 
propagation, which may turn some capturing lambdas into non-capturing 
ones (big win already), and further expose them to condy-ization and 
therefore deduplication.