Clear the whole structure

Property definitions

core $ HashCollection :: raz
	# Clear the whole structure
	fun raz
	do
		var i = _capacity - 1
		while i >= 0 do
			_array[i] = null
			i -= 1
		end
		_the_length = 0
		_first_item = null
		_last_item = null
		_last_accessed_key = null
	end
lib/core/collection/hash_collection.nit:156,2--168,4