Merge res_timing_pthread. This is a timing interface for Asterisk that

Merge res_timing_pthread.  This is a timing interface for Asterisk that
does not require DAHDI.  It's called "pthread" because it uses a pthread
API call in the timing thread for sleeping and ensuring we wake up at
an appropriate time.  I wasn't sure what else to call it.  :)

The timing API requires a file descriptor that can be polled on.  So,
when you open a timer, this module creates a pipe and returns the read
end of the pipe.  There is a background thread that wakes up every 10ms
and checks to see if any of the currently open timers need a 'tick' and
writes to the appropriate pipe.

git-svn-id: http://svn.digium.com/svn/asterisk/trunk@122928 614ede4d-c843-0410-af14-a771ab80d22e