Explicit constructors for deadline handler and timer

libuavcan/include/uavcan/scheduler.hpp

@@ -19,7 +19,7 @@ class MonotonicDeadlineHandler : public LinkedListNode<MonotonicDeadlineHandler>
 protected:
     Scheduler& scheduler_;
 
-    MonotonicDeadlineHandler(Scheduler& scheduler)
+    explicit MonotonicDeadlineHandler(Scheduler& scheduler)
     : monotonic_deadline_(0)
     , scheduler_(scheduler)
     { }

libuavcan/include/uavcan/timer.hpp

@@ -42,7 +42,7 @@ public:
     using MonotonicDeadlineHandler::getMonotonicDeadline;
     using MonotonicDeadlineHandler::getScheduler;
 
-    Timer(Scheduler& scheduler)
+    explicit Timer(Scheduler& scheduler)
     : MonotonicDeadlineHandler(scheduler)
     , period_(InfinitePeriod)
     { }