ITERATIVE-DEEPENING-SEARCH is a shell around the DEPTH-LIMITED-SEARCH that calls the DEPTH-LIMITED-SEARCH with increasingly large depth limits.  It increments the depth limit by 1 each time.
	To think about: ITERATIVE-DEEPENING-SEARCH only increases by one each time, which leads to overhead.  However, we’ve shown in class that the overhead can be relatively small compared to the final cost.  Still, would increasing this rate be useful in some configurations?