Use monotonic clock source for Windows in oic_time

Use monotonic clock source for Windows in oic_time

Amend documentation of OICGetCurrentTime() function.

We must replace our GetSystemTimeAsFileTime API call because system
time updates should not impact our calculations. We should assume that
system time can change during the runtime of our programs.

Change-Id: I49246a243435f8b0b2bf7a77fcb31378dc921daf
Signed-off-by: David Antler <david.a.antler@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/9333
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jon A. Cruz <jon@joncruz.org>