signal_eintr.py: More complete patch, modify also signal.sigwaitinfo().

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I don't think that other signal functions need to be modified to handle EINTR.

POSIX manual pages:
- "The pthread_sigmask() function shall not return an error code of [EINTR]."
- "The pthread_kill() function shall not return an error code of [EINTR]."

pause() fails with EINTR when it receives a signal, but signal.pause() doesn't raise InterruptedError in this case, it only returns None, because we expect a signal.

I tested: signal.sigwait([]) doesn't fail with EINTR with a signal is received. No need to modify this function.

On Linux, signal.set_wakeup_fd() doesn't fail with InterruptedError.