yesod::rope: overhaul to use new counted_ptr<> (7)

joined_range<> is still broken.

Signed-off-by: Alex Dubov <oakad@yahoo.com>
yesod::rope: overhaul to use new counted_ptr<> (8)

Remove dependency on iterator ranges as unhelpful.

Signed-off-by: Alex Dubov <oakad@yahoo.com>