belopolsky will be happy to see this new version of my patch:
- datetime.totimestamp() => (seconds, microseconds): two integers
- datetime.totimestamp() implement don't use Python time.mktime() but
directly the C version of mktime() because time.mktime() creates a
float value
- fix time.mktime() to support the timestamp -1 (first second before
the epoch) to make it consistent with datetime.totimestamp() which
also support this value
- fix documentation: it's microseconds (10^-6) and not milliseconds
(10^-3)