Fix 6 warnings from win64, where one is a potential bug.

sql/event_data_objects.cc:
  Passing time as time_t to function my_time_t requires
  cast to my_time_t since my_time_t are only required to be 32bits.
sql/log.cc:
  Using time_t instead of my_time_t when calculating current_time.
  This is a potential bugfix for problem with mysql_system_db reporting
  slow log as crashed.
sql/sql_show.cc:
  Passing time as time_t to function my_time_t requires
  cast to my_time_t since my_time_t are only required to be 32bits.

sql/event_data_objects.cc

@@ -535,7 +535,7 @@ Event_parse_data::init_ends(THD *thd)
     Check whether ENDS is not in the past.
   */
   DBUG_PRINT("info", ("ENDS after NOW?"));
-  my_tz_UTC->gmt_sec_to_TIME(&ltime_now, thd->query_start());
+  my_tz_UTC->gmt_sec_to_TIME(&ltime_now, (my_time_t)thd->query_start());
   if (my_time_compare(&ltime_now, &ltime) == 1)
     goto error_bad_params;
 
@@ -1266,7 +1266,7 @@ Event_queue_element::compute_next_execution_time()
     goto ret;
   }
 
-  my_tz_UTC->gmt_sec_to_TIME(&time_now, current_thd->query_start());
+  my_tz_UTC->gmt_sec_to_TIME(&time_now, (my_time_t)current_thd->query_start());
 
   DBUG_PRINT("info",("NOW: [%lu]",
                      (ulong) TIME_to_ulonglong_datetime(&time_now)));

sql/log.cc

@@ -899,7 +899,7 @@ bool LOGGER::slow_log_print(THD *thd, const char *query, uint query_length,
   bool is_command= FALSE;
   char user_host_buff[MAX_USER_HOST_SIZE];
 
-  my_time_t current_time;
+  time_t current_time;
   Security_context *sctx= thd->security_ctx;
   uint user_host_len= 0;
   longlong query_time= 0, lock_time= 0;

sql/sql_show.cc

@@ -3981,20 +3981,21 @@ static void store_schema_partitions_record(THD *thd, TABLE *schema_table,
   if (stat_info.create_time)
   {
     thd->variables.time_zone->gmt_sec_to_TIME(&time,
-                                              stat_info.create_time);
+                                              (my_time_t)stat_info.create_time);
     table->field[18]->store_time(&time, MYSQL_TIMESTAMP_DATETIME);
     table->field[18]->set_notnull();
   }
   if (stat_info.update_time)
   {
     thd->variables.time_zone->gmt_sec_to_TIME(&time,
-                                              stat_info.update_time);
+                                              (my_time_t)stat_info.update_time);
     table->field[19]->store_time(&time, MYSQL_TIMESTAMP_DATETIME);
     table->field[19]->set_notnull();
   }
   if (stat_info.check_time)
   {
-    thd->variables.time_zone->gmt_sec_to_TIME(&time, stat_info.check_time);
+    thd->variables.time_zone->gmt_sec_to_TIME(&time,
+                                              (my_time_t)stat_info.check_time);
     table->field[20]->store_time(&time, MYSQL_TIMESTAMP_DATETIME);
     table->field[20]->set_notnull();
   }