OPTIONAL
SYNOPSIS
	mixed * intersect_alist (mixed * list1, mixed * list2)

DESCRIPTION
	Does a fast set intersection on alist key vectors (NOT on full alists!).
	The operator '&' does set intersection on arrays in general.

EXAMPLE
	new_list = intersect_alist(list1, list2);

SEE ALSO
	filter_array(E), assoc(E), insert_alist(E), map_array(E),
	member_array(E), order_alist(E), sort_array(E), unique_array(E)
