Resolves #160 by resync of clock

Could be improved by not doing every frame and by ensuring that the clock sync can't be starved from happening. It does not, in principle, allow for different machines to clock sync without restart. One bug may not may not be related to this which causes the program to crash on peer disconnect (client stream removal).

components/common/cpp/include/ftl/timer.hpp

@@ -80,7 +80,7 @@ void setClockAdjustment(int64_t ms);
  * If all high precision callbacks together take more than 1ms to complete, a
  * warning is produced.
  */
-const TimerHandle add(timerlevel_t, const std::function<void(int64_t ts)> &);
+const TimerHandle add(timerlevel_t, const std::function<bool(int64_t ts)> &);
 
 /**
  * Initiate the timer and optionally block the current process.
@@ -92,6 +92,8 @@ void start(bool block=false);
  */
 void stop(bool wait=true);
 
+size_t count(timerlevel_t);
+
 /**
  * Stop and clear all callbacks. Used for testing purposes.
  */