all: Refactoring work with time using boost::chrono

Now the library has two clocks: time::steady_clock and
time::system_clock, following (boost|std)::chrono.  In addition to
standard now() method, the library contains several helpers to convert
to/from UnixTimestamp (microsecond resolution) and IsoString (optional
microsecond resolution).  The IsoString conversions use
boost::posix_time routines, since boost::chrono supports extended IO
support only starting boost version 1.52 (Boost Chrono V2).

This commit breaks compatibility with previous API.  All time-related
Data/Interest calls must explicitly use time units to specify
FreshnessPeriod/InterestLifetime.

Brief usage/conversion guide:

- creation of time units does not support double/float types.  If
  necessary to create time unit from double, ``ndn::duration<double>`` (for
  seconds) needs to be used instead.  In some cases, this would also
  require ``ndn::duration_cast``, if the target is not ``ndn::nanoseconds``.
- ndn::getNow, ndn::ndn_getNowMilliseconds, ndn::time::now are all
  removed in favor of the now() method in a specific clock:

    * time::system_clock::now();
    * time::steady_clock::now();

- When necessary to convert system_clock::TimePoint to unix timestamp,
  ``time::toUnixTimestamp`` can be used.  This method return number of
  milliseconds since UNIX epoch as ``ndn::time::milliseconds`` type.
  Use count() method to obtain number as an integral value.

Change-Id: Icd688bc6766e008d60c3d2888173627874526e47
Refs: #1152
diff --git a/src/util/monotonic_deadline_timer.hpp b/src/util/monotonic_deadline_timer.hpp
index 3cfb05f..2b1558d 100644
--- a/src/util/monotonic_deadline_timer.hpp
+++ b/src/util/monotonic_deadline_timer.hpp
@@ -17,20 +17,20 @@
 namespace boost {
 namespace asio {
 
-template <> 
-struct time_traits<ndn::time::monotonic_clock>
+template <>
+struct time_traits<ndn::time::steady_clock::TimePoint::clock>
 {
-  typedef ndn::time::Point time_type;
-  typedef ndn::time::Duration duration_type;
+  typedef ndn::time::steady_clock::TimePoint time_type;
+  typedef ndn::time::steady_clock::TimePoint::clock::duration duration_type;
 
   static time_type
   now()
   {
-    return ndn::time::now();
+    return ndn::time::steady_clock::now();
   }
 
   static time_type
-  add(const time_type& time, const duration_type& duration) 
+  add(const time_type& time, const duration_type& duration)
   {
     return time + duration;
   }
@@ -50,13 +50,25 @@
   static boost::posix_time::time_duration
   to_posix_duration(const duration_type& duration)
   {
-    return boost::posix_time::microseconds(duration/1000);
+    return
+#ifdef BOOST_DATE_TIME_HAS_NANOSECONDS
+      boost::posix_time::nanoseconds(
+        ndn::time::duration_cast<ndn::time::nanoseconds>(duration).count())
+#else
+      boost::posix_time::microseconds(
+        ndn::time::duration_cast<ndn::time::microseconds>(duration).count())
+#endif
+      ;
   }
 };
 
-typedef basic_deadline_timer<ndn::time::monotonic_clock> monotonic_deadline_timer; 
-
 } // namespace asio
 } // namespace boost
 
+namespace ndn {
+
+typedef boost::asio::basic_deadline_timer<time::steady_clock::TimePoint::clock> monotonic_deadline_timer;
+
+} // namespace ndn
+
 #endif // NDN_UTIL_MONOTONIC_DEADLINE_TIMER_HPP