Fix VC++ compiler error with redifinition return type

include/thr_alarm.h

@@ -100,7 +100,7 @@ typedef struct st_alarm {
 #define thr_alarm_init(A) (*(A))=0
 #define thr_alarm_in_use(A) (*(A)!= 0)
 void init_thr_alarm(uint max_alarm);
-bool thr_alarm(thr_alarm_t *alarmed, uint sec, ALARM *buff);
+my_bool thr_alarm(thr_alarm_t *alarmed, uint sec, ALARM *buff);
 void thr_alarm_kill(pthread_t thread_id);
 void thr_end_alarm(thr_alarm_t *alarmed);
 void end_thr_alarm(my_bool free_structures);