'function' supported in the fmt

[yangluoshen]

clog is really tiny and easy-use.
I found a comfortable-look way for clog fmt, and add function option for that.
#define CLOG_DEFAULT_FORMAT "%d %t [%l][%F]%m[%f(%n)]\n
while looks like following:

2017-05-24 08:32:01 [DEBUG][proc_cru_msg]msgtype[1][phu.c(21)]
2017-05-24 08:32:01 [DEBUG][fsm_entity_start_timer]start timer,fsmid[51],timerid[0],second[-1][fsm.c(244)]
2017-05-24 08:32:01 [DEBUG][fsm_entity_start_timer]start timer success,timerid[0][fsm.c(260)]
2017-05-24 08:32:01 [DEBUG][fsm_entity_start_timer]start timer,fsmid[51],timerid[5],second[4][fsm.c(244)]
2017-05-24 08:32:01 [DEBUG][start_timer]start timer[7] success[main.c(332)]
2017-05-24 08:32:01 [DEBUG][fsm_entity_start_timer]start timer success,timerid[5][fsm.c(260)]
2017-05-24 08:32:01 [DEBUG][philos_think]---Allen thinking---[philosfsm.c(27)]
2017-05-24 08:32:01 [DEBUG][proc_fsm_req]Exit.[fsm.c(316)]
2017-05-24 08:32:02 [DEBUG][proc_cru_msg]msgtype[1][phu.c(21)]