minor comment changes, code rearrangement and field renaming

to minimize diffs with future modifications.

The current implementation is problematic for the following reasons:
+ all insertions are O(N) because the event list does not have a tail
  pointer;
+ there is only a single lock protecting both session and users queues.
+ the implementation of the queue itself is not documented.
  I think i have figured it out, more or less, but am unclear on
  whether there is proper locking in place

The rewrite (which i have working locally) uses a tailq so insertions
are O(1), separate locks for the event and session queues, and has
a documented implementation so hopefully we can figure out if/where
bug exist.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@45753 65c4cc65-6c06-0410-ace0-fbb531ad65f3