Return SizedIteratorRanges from ranges::range for RandomAccessIteratorRanges and SizedIterables

The interface of `ranges::range` consists of:

- `ranges::range(Iterator, Sentinel, Size) -> sized_iterator_range`
- `ranges::range(Iterator, Sentinel) -> iterator_range`

However, when calling `ranges::range(Iterator, Sentinel)` with `RandomAccessIterator`s, we can 
compute the range size in `O(1)` and return a `sized_iterator_range`.

Furthermore, some containers like `std::list` provide only `BidirectionalIterator`s, but they have
an `O(1)` `size()` member function.

This patch changes `ranges::range` interface to: 

- `ranges::range(Iterator, Sentinel, Size) -> sized_iterator_range`
- `ranges::range(Iterator, Sentinel) -> sized_iterator_range` (if possible) / `iterator_range`
- `ranges::range(Iterable&) -> sized_iterator_range` (if possible) / `iterator_range`

The `ranges::range(Iterable&)` dispatches to a `sized_iterator_range` if the `Iterable` has `RandomAccessIterator`s or `ranges::size(Iterable&)` can compute its size (which is `O(1)`). Otherwise it returns an `iterator_range`.

Note:  the `algorithm/equal.cpp` test used to perform one comparison in the modified `CHECK` clause when comparing two `RandomAccessRange`s even tho they had different sizes. Now it doesn't need to perform any comparison at all. 
> Which I think brings us back to the original issue - do we want a find_size() operation to eliminate this cast?

We have `size`. I don't see a need for `find_size`.

> It is generally useful (I see a lot of distance() followed by cast calls).

In my code, or in this pull request? Gonzalo didn't know the ins and outs of my code when he made the pull request we're commenting on. I closed this pull request since it's not needed.