Updating handling of memoization

library/lazy/package.scala

src/main/scala/leon/laziness/LazinessEliminationPhase.scala

src/main/scala/leon/laziness/LazinessUtil.scala

src/main/scala/leon/laziness/LazyClosureConverter.scala

...s/lazy-datastructures/memoization/FibonacciMemoized.scala

testcases/lazy-datastructures/memoization/Knapsack.scala