Include miliseconds in logging

Hi!

Sorry for this stupid question, but my C skills are very poor and I'm
not being able to do this correctly...

I want to be able to see miliseconds on my logs, something like having
this in gwlib/log.c


sprintf(p, "%04d-%02d-%02d %02d:%02d:%02d (%d)",
        tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
        tm.tm_hour, tm.tm_min, tm.tm_sec, tm.tm_usec);


where I added a "(%d)" and "tm.tm_usec"

but I'm not sure where I have to modify the tm struct to include tm_usec
can anyone guide me on where to modifiy this?

thnx in advance,

Juan