Changed list length to size_t.
Renamed pact_linkedlist_create to pact_linkedlist_new.
Renamed pact_linkedlist_destroy to pact_linkedlist_free.
Fixed a memory leak where popped nodes in pact_linkedlist_popfront were not freed.
Fixed a bug where when a value is popped from popfront the next head node's "prev" value was not set to null and would keep it's link to the free'd node.
In addition popfront now returns the popped value.
Fixed a memory leak where popped nodes in pact_linkedlist_popback were not freed.
Fixed a bug where when a value is popped from popback the next tail node's "next" value was not set to null and would keep it's link to the free'd node.
In addition popback now returns the popped value.
Fixed a bug in pact_linked_list_pushfront.  New node's prev field was not set to NULL.
Fixed a bug in pact_linked_list_pushfront.  Error codes were swapped returning false for success and non zero for failure.
Fixed a bug in pact_linked_list_pushback.  New node's next field was not set to NULL.
Fixed a bug in pact_linked_list_pushback.  Error codes were swapped returning false for success and non zero for failure.
Added iterators to pact_LinkedList.
Updated code base to reflect changes to pact_LinkedList.
Merge pull request #3 from brenttaylor/linked_list_rework

Linked list rework