This module implements FIFO queues in an efficient manner.
Queue = queue()Returns an identifier for the queue.
Item = term()Q1 = Q2 = queue()Inserts Item into the queue Q1. Returns a new queue Q2.
Result = {{value, Item}, Q1} | {empty, Q2}Q = Q1 = Q2 = queue()Removes the oldest element from the queue Q.
Returns the tuple {{value, Item}, Q2}, where Item is
the element removed and Q1 is an identifier for the new queue.
If Q is empty, the tuple {empty, Q2} is returned.