RedHatTransformer: Fix a few missing tokens
RedHatTransformer: Don’t produce empty arg lists

The RedHat compiler’s parser never produces empty SequentialArguments,
it assigns null instead to the containing nodes (tuple and iterable
literals, named argument lists). We should emulate that behavior (for
example, ceylon.formatter even has an assertion for it).
Test completeCompilationUnit compilation as well

Using ceylon.formatter.