Fix my_system_gmt_sec function declaration to be same as definition

sql-common/my_time.c:
  Function declaration must be same as definition

sql-common/my_time.c

@@ -780,7 +780,7 @@ long calc_daynr(uint year,uint month,uint day)
 */
 my_time_t
 my_system_gmt_sec(const MYSQL_TIME *t_src, long *my_timezone,
-                  bool *in_dst_time_gap)
+                  my_bool *in_dst_time_gap)
 {
   uint loop;
   time_t tmp= 0;