MT#40962 allow for varying sleep times

We may end up sleeping shorter or longer than the desired sleep time. If
we ended up sleeping shorter, don't advance a tick, and if we ended up
sleeping significantly longer (more than one tick), advance multiple
ticks.

Change-Id: I0be20104e6243c89006367430a3663cc304486b9

core/sip/wheeltimer.cpp

@@ -88,8 +88,12 @@ void _wheeltimer::run()
     //printf("missed one tick\n");
     //}
 
-    turn_wheel();
-    next_tick += tick;
+    now = gettimeofday_us();
+
+    while (now >= next_tick) {
+      turn_wheel();
+      next_tick += tick;
+    }
   }
 }