* Specialize ins1() into app1() for appends.  Saves several unnecessary   steps and further improves the speed of list append.
* Specialize ins1() into app1() for appends.  Saves several unnecessary
  steps and further improves the speed of list append.

* Add guards to the list iterator length method to handle corner cases.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator