Initial patch by Larry Hastings.

Patch by Elvis Pranskevichus

It was very much outdated, and the topic is better covered elsewhere.

Overflow test in test_FromSecondsObject() fails on FreeBSD 10.0 buildbot which
uses clang. clang implements more aggressive optimization which gives
different result than GCC on undefined behaviours.

Check if a multiplication will overflow, instead of checking if a
multiplicatin had overflowed, to avoid undefined behaviour.

Add also debug information if the test on overflow fails.

Use volatile keyword in _PyTime_AsSecondsDouble()

Use volatile keyword in _PyTime_Round()

Filter also values for check_float_rounding().

Filter values which would overflow when converted to a C time_t type.

* Filter values which would overflow on conversion to the C long type
  (for timeval.tv_sec).
* Adjust also the message of OverflowError on PyTime conversions
* test_time: add debug information if a timestamp conversion fails

(About the only new feature that was worth mentioning in
whatsnew without a NEWS entry)

boolean result instead of raising an exception.

Patch by A Kaptur.