Merge to STABLE

Fixed two bugs:
* #1035575 from SourceForge (by adding smart constructors for source tuple
  construction at value and type level)
* Parallel array comprehensions were handled wrongly
  - The singleton expression-pattern pair `()'-`[:():]' is the neutral element
    for cross products (comma notation in comprehensions), but not for
    parallel comprehensions.
  - Now groups of parallel statements are handled separately (which is more
    like the vanilla list comprehension case).
  - The code is too general in that it correctly handles cross-products of
    groups of parallel qualifiers.  As this is correctly handled in the
    list and the array comprehension case, the syntax may be generalised to
    allow arbitrary nesting of cross-products and parallel qualifiers.