Return a new iteralot on all couples

Used to provide iterator and others

Property definitions

core $ CoupleMap :: couple_iterator
	# Return a new iteralot on all couples
	# Used to provide `iterator` and others
	protected fun couple_iterator: Iterator[Couple[K,V]] is abstract
lib/core/collection/abstract_collection.nit:1280,2--1282,65

core $ ArrayMap :: couple_iterator
	redef fun couple_iterator do return _items.iterator
lib/core/collection/array.nit:722,2--52