sock_call_ex() gets the socket error code when the socket function fails.
sock_connect_impl() didn't set the error correctly.

instead of raising InterruptedError if the connection is interrupted by
signals, signal handlers don't raise an exception and the socket is blocking or
has a timeout.

socket.socket.connect() still raise InterruptedError for non-blocking sockets.

Patch by Martin Panter.

Patch by Martin Panter.

Patch by Cédric Krier.

sock_send_impl()

The BEGIN_SELECT_LOOP and END_SELECT_LOOP macros of socketmodule.c don't handle
EINTR. Functions using these macros use an inner loop to handle EINTR, but they
don't recompute the timeout.

This changes replaces the two macros with a new sock_call() function which
takes a function as a parameter. sock_call() recomputes the timeout, handle
false positive and handle EINTR.

to its signal handlers.

Use also _Py_write_noraise() instead of write() to retry write() if it is
interrupted by a signal (fail with EINTR).

faulthandler.dump_traceback() also calls PyErr_CheckSignals() to call the
Python signal handler if a signal was received.

and _Py_DumpTracebackThreads(). Document also these functions to explain that
the caller is responsible to call PyErr_CheckSignals().

_posixsubprocess

signalmodule.c

Helper to write() which retries write() if it is interrupted by a signal (fails
with EINTR).

_PyTime_AsMicroseconds() rounding.

Add also unit tests.

MemoryError.

MemoryError.

multiple threads.

multiple threads.

Windows uses WSAEINTR error code, not EINTR, for socket functions.

Patch by Martin Panter.

Call PyErr_CheckSignals() immediatly if connect() or select() fails with EINTR
in internal_connect().

Refactor also the code to limit indentaton and make it more readable.