*Applies to last patch also!*
Remove duplicate code in iterators. We used to have separate iterator
and const_iterator but now they are the same class with some enable_if
magic to disable references from const_iterator
This introduces some 'bad things' you can for example call
const_iterator.operator*<false>() to obtain non const reference. I
don't think this matters since you could use const_cast or something
else to work around const if you really tried
338771c5b0