[Gecode] Operations on iterators

[Christian Schulte]

In iter/ranges-operations.hh are some operations on iterators such as
computing the size, testing for equality, subset, disjointness and so on.

I saw that these operations are actually needed for the set stuff, however
there you have hilarious and inefficient variants of testing for subset and
disjointness by using intersection or difference.

Please fix that (and check whether the operations are actually ok) and
please remove all the stuff from iter-basic.hh that is not longer needed
there.

Christian

--
Christian Schulte, http://www.imit.kth.se/~schulte/