Introducing right folds for ppmpf collections (tuples, sequences).

By introducing a tuple / sequence reversal function macro, ppmpf can now
provide for right folds as well. Finished transition to balanced parentheses
return from fold algorithms and applied fixes to headers using them. From now
on, ppmpf tuples / sequences are to be referred to as "collections". Notice
that folding over a collection will always return a parenthesis enclosed
preprocessor token.