The python and c implementation of bisect do not support custom-sorted lists using the list.sort method.

In order to support an arbitrarily sorted list via sort(cmp, key, reverse), I have added 3 corresponding parameters to the bisect methods for bisection and insort (insert-sorted) corresponding to the parameters in sort.  This would be useful if a list is initially sorted by its sort method and then the client wishes to maintain the sort order (or reverse-sort order) while inserting an element.  In this case, being able to use the same, arbitrary binary function cmp, unary function key and boolean reverse flag to preserve the list order.

The change imposes 3 new branch conditions and potential no-op function calls for when key is None.  I have here implemented and partially tested the python implementation and if someone besides me would find this useful, I will update the _bisectmodule.c for this change as well.

The Heap functions may also find use of an arbitrary predicate function so I may look at that later, but because bisect goes hand in hand with sorting, I wanted to tackle that first.