Get rid of struct Time

We just need the milliseconds of current system
time for our needs. This allows to simplify the
API.

No functional change.

src/misc.h

@@ -44,15 +44,10 @@ struct Log : public std::ofstream {
 };
 
 
-struct Time {
-  int64_t msec() const { return time_to_msec(t); }
-  int elapsed() const { return int(now().msec() - msec()); }
-
-  static Time now() { Time t; system_time(&t.t); return t; }
-
-private:
-  sys_time_t t;
-};
+namespace Time {
+  typedef int64_t point;
+  point now();
+}
 
 
 template<class Entry, int Size>