On the serf-195 branch: Update request list docstrings.

* src/outgoing_request.c
  (serf__reqlist_push): The requst is added to the tail of the list.
  (serf__reqlist_peek): Returns the request at the head of the list.


git-svn-id: https://svn.apache.org/repos/asf/serf/branches/SERF-195@1935104 13f79535-47bb-0310-9956-ffa450edef68