Add kqueue(2) implementation to Asterisk in various places.

This will save a considerable amount of CPU on the BSDs, including Mac OS X,
as it eliminates several places in the code that we previously used a busy
loop.  Additionally, this adds a res_timing interface, using kqueue timers.

Review: https://reviewboard.asterisk.org/r/543/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@262852 65c4cc65-6c06-0410-ace0-fbb531ad65f3