* Replace "time.clock on windows, or time.time" with time.perf_counter()
* profile module: only use time.process_time() instead of trying different
functions providing the process time
* timeit module: use time.perf_counter() by default, time.time() and
time.clock() can still be used using --time and --clock options
* pybench program: use time.perf_counter() by default, add support for
the new time.process_time() and time.perf_counter() functions, but stay
backward compatible. Use also time.get_clock_info() to display information
of the timer.
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