Issue #1670: Remove the optimization for loops over stepped ranges and fix the optimization for loops over ranges to use the new Enumerable contract.
Issue #1670: Add a simple benchmark for Range iteration.
Issue #1670: Fix some tests to do with optimized Range iteration.
Issue #1670: Adjust optimization tests now we no longer optimize stepped range iteration
Issue #1670 (also ceylon/ceylon-spec#451): Update other tests for the new Enumerable and Range.