Fix compilation on Windows broken with the push of bug#16420.

Fix three compilation warnings.

sql/event_data_objects.cc

@@ -1293,7 +1293,7 @@ bool get_next_time(const Time_zone *time_zone, my_time_t *next,
       time, and this will greatly reduce the effect of the
       optimization.  So instead we keep the code simple and clean.
     */
-    interval.month= diff_months - diff_months % months;
+    interval.month= (ulong) (diff_months - diff_months % months);
     next_time= add_interval(&local_start, time_zone,
                             INTERVAL_MONTH, interval);
     if (next_time == 0)
@@ -1301,7 +1301,7 @@ bool get_next_time(const Time_zone *time_zone, my_time_t *next,
 
     if (next_time <= time_now)
     {
-      interval.month= months;
+      interval.month= (ulong) months;
       next_time= add_interval(&local_start, time_zone,
                               INTERVAL_MONTH, interval);
       if (next_time == 0)

sql/event_queue.cc

@@ -65,13 +65,10 @@ struct event_queue_param
 static int 
 event_queue_element_compare_q(void *vptr, byte* a, byte *b)
 {
-  /*
-    Note that no overflow is possible here because both values are
-    non-negative, and subtraction is done in the signed my_time_t
-    type.
-  */
-  return (((Event_queue_element *)a)->execute_at
-          - ((Event_queue_element *)b)->execute_at);
+  my_time_t lhs = ((Event_queue_element *)a)->execute_at;
+  my_time_t rhs = ((Event_queue_element *)b)->execute_at;
+
+  return (lhs < rhs ? -1 : (lhs > rhs ? 1 : 0));
 }
 
 
@@ -580,8 +577,7 @@ Event_queue::get_top_for_execution_if_time(THD *thd,
         time or until signaled. Release LOCK_queue while waiting.
       */
       struct timespec top_time;
-      top_time.tv_sec= next_activation_at;
-      top_time.tv_nsec= 0;
+      set_timespec(top_time, next_activation_at - thd->query_start());
       cond_wait(thd, &top_time, queue_wait_msg, SCHED_FUNC, __LINE__);
 
       continue;