Create a max_time too

This is helpful for matching with min_time.

Change-Id: I247a43027777843f1d3fe41ed8b857abc1a80a54
diff --git a/aos/time/time.h b/aos/time/time.h
index 136629c..0333c5c 100644
--- a/aos/time/time.h
+++ b/aos/time/time.h
@@ -37,6 +37,8 @@
 
   static constexpr time_point min_time{
       time_point(duration(::std::numeric_limits<duration::rep>::min()))};
+  static constexpr time_point max_time{
+      time_point(duration(::std::numeric_limits<duration::rep>::max()))};
 };
 
 class realtime_clock {
@@ -60,6 +62,8 @@
 
   static constexpr time_point min_time{
       time_point(duration(::std::numeric_limits<duration::rep>::min()))};
+  static constexpr time_point max_time{
+      time_point(duration(::std::numeric_limits<duration::rep>::max()))};
 };
 
 namespace time {