lambda: unit test for lambda expressions at Java Language source level.

Rationale: having a checkers-flavored unit test will enable testing
           both if the correct HIR is generated using the checker
           as well as the correctness of execution (interpreter for now,
           but native code later).

Change-Id: I588e9955efaaf53e5c5e3398399e009041cd65f0
5 files changed