+# changes:
+# 1. Timer::Timer ---> Timer
+# 2. timer id is now the object_id of the action
+# 3. Timer resolution removed, we're always arbitrary precision now
+# 4. I don't see any obvious races [not that i did see any in old impl, though]
+# 5. We're tickless now, so no need to jerk start/stop
+# 6. We should be pretty fast now, wrt old impl
+# 7. reschedule/remove/block now accept nil as an action id (meaning "current")
+# 8. repeatability is ignored for 0-period repeatable timers
+# 9. configure() method superceeds reschedule() [the latter stays as compat]