Timestamp Log Detailing

Timestamp is added at the head of each log line.
I abandoned the previous apprach which replacing the talk_base
logging class.
This time, I used macro to replace LOG_TS with LOG with timestap.
To the best of my knowledge, libjingle does not provide wall time
clock utils, but only process or O/S clock tick. So CurrentTime class is
added in new file tincan_utils.