* ctrace.h (class CTrace): Add new field clock_real_ to record the REAL clock.
(CTrace::Submit): Calculate the duration from real clock. Advance the duration
if necessary.
We calculate the real duration to avoid the situation like this:
A lot of call of small function happen before the current function,
which will eat up the duration if using the old algorithm.
We advance the duration to avoid the situation like this:
This function contains a lot of small calls, but the real duration
is small. But we needs to expand the duration of this function.
For each small calls uses up at least 0.001ms, but in fact they may
use less than 0.001ms at sum. So the expansion is needed.