* Add Lib/test/signalinterproctester.py
* Don't disable the garbage collector anymore
* Don't use os.fork() with a subprocess to not inherit existing signal handlers
  or threads: start from a fresh process
* Don't use UNIX kill command to send a signal but Python os.kill()
* Use a timeout of 10 seconds to wait for the signal instead of 1 second
* Always use signal.pause(), instead of time.wait(1), to wait for a signal
* Use context manager on subprocess.Popen
* remove code to retry on EINTR: it's no more needed since the PEP 475
* remove unused function exit_subprocess()
* Cleanup the code

Patch by Christie Wilson.

I have compared output between pre- and post-patch runs of these tests
to make sure there's nothing missing and nothing broken, on both
Windows and Linux.  The only differences I found were actually tests
that were previously *not* run.

signal handler does not raise an exception

when interrupted by a signal not in the *sigset* parameter, if the signal
handler does not raise an exception. signal.sigtimedwait() recomputes the
timeout with a monotonic clock when it is retried.

Remove test_signal.test_sigwaitinfo_interrupted() because sigwaitinfo() doesn't
raise InterruptedError anymore if it is interrupted by a signal not in its
sigset parameter.

retried with the recomputed delay, except if the signal handler raises an
exception (PEP 475).

Modify also test_signal to use a monotonic clock instead of the system clock.

Sorry, it was a mistake, the patch is still under review: issue #23646.

descriptor is in blocking mode.

A side effect is that Python depends to the WinSock library.

set the blocking mode of a file descriptor (False if the O_NONBLOCK flag is
set, True otherwise). These functions are not available on Windows.

assertIs().

ValueError on fstat() failure.

- Use _testcapi.raise_signal() in test_signal
- close also os.pipe() file descriptors in some test_signal tests where they
  were not closed properly
- Remove faulthandler._sigill() and faulthandler._sigbus(): reuse
  _testcapi.raise_signal() in test_faulthandler

Report and patch by Vajrasky Kok.

(trying to fix a failure on the FreeBSD 9.0 buildbot)

Issue #16105: When a signal handler fails to write to the file descriptor registered with ``signal.set_wakeup_fd()``, report an exception instead of ignoring the error.

signal.getsignal returns None for some signals if faulthandler
is enabled (Patch by Jeremy Kloth)

sigwaitinfo() can be interrupted on Linux (raises InterruptedError), but not on
AIX.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

Add a private API to convert an int or float to a C timespec structure.

real-time signals.

When signals are unblocked, pending signal ared delivered in the reverse order
of their number (also on Linux, not only on FreeBSD 6).

Don't sort signals by their number if signals were not blocked (test_signum).