Add support for "absolute" timeouts, which are expressed relative to
system uptime instead of deltas from current time. These allow for
more race-resistant code to be written by allowing application code to
do a single timeout computation, once, and then reuse the timeout
value even if the thread wakes up and needs to suspend again later.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
4c7b77a716