Rename deque to deque_linkedlist, in preparation of adding other deque implentations.
Make the name of the templates configurable.
Add empty implementation of deque with circular buffer.
Implement circular buffer deque, for now only pushback and popfront (missing popback and pushfront).
Add many asserts in deque_circbuf, add mechanism to detect calls made on destructed objects.
Improve asserts in deque_circbuf.
Implement proper buffer resizing for deque_circbuf.
Remove constraint that mem is zeroed in deque_circbuf, fix prob. with push/pop to/from empty.