[iter] Simplify operator!= of iterator filters

Both to save ops, and also because lambdas don't implement operator!=,
so this was failing in range-based for loop if a lambda was passed to
hb_map() or hb_filter().  Just check end-condition assuming that we
are comparing to .end() or iterators that are otherwise derived from
current iterator.  Ie. don't compare things that are expected to be
in common.
1 file changed