This patch changes the scheduler to use a max-heap to store pending scheduler
entries instead of a fully sorted doubly linked list. When the number of
entries in the scheduler gets large, this will perform much better. For much
more detailed information on this change, see the review request.
Review: http://reviewboard.digium.com/r/160/
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@176639 65c4cc65-6c06-0410-ace0-fbb531ad65f3
