Before this commit we had two statements blocks for 'for' loops:
range variable declaration + iterator variable declaration + while loop.
However, BE requires a bit different loop structure to make lowerings
properly so in this commit iterator declaration & while loop were
extracted to separate block.
* fixed NoSuchMethod caused by mismatched signatures of the "invoke" method generated for lambda arguments
* added test cases in invoke.kt for KFunction and anonymous functions
* added a transformer to wrap the last expression in the bodies of lambdas with return
Mikhail Glukhikh