poll tests: Avoid test failure on native Windows

[Bruno Haible]

On native Windows, I see the 'test-poll' test fail always:

FAIL: test-poll
===============

Unconnected socket test... passed
Connected sockets test... passed
General socket test with fork... passed
Pipe test... failed (expecting POLLHUP after shutdown)
FAIL test-poll.exe (exit status: 1)

Since our documentation says that POLLHUP is not fixed by this module
anyway (it does not work on AIX either), let me disable this part of the
test.


2023-04-25  Bruno Haible  <br...@clisp.org>

        poll tests: Avoid test failure on native Windows.
        * tests/test-poll.c (test_pipe): Disable the POLLHUP check also on
        native Windows.
        * doc/posix-functions/poll.texi: Mention also native Windows w.r.t.
        POLLHUP.

diff --git a/doc/posix-functions/poll.texi b/doc/posix-functions/poll.texi
index 1fad8f85a9..ab7083c1c0 100644
--- a/doc/posix-functions/poll.texi
+++ b/doc/posix-functions/poll.texi
@@ -26,5 +26,5 @@
 @item
 On some platforms, file descriptors other than sockets do not support
 POLLHUP; they will return a "readable" or "writable" status instead:
-AIX 7.2, HP NonStop.
+AIX 7.2, HP NonStop, mingw, MSVC.
 @end itemize
diff --git a/tests/test-poll.c b/tests/test-poll.c
index 716c38b492..f34f7f460a 100644
--- a/tests/test-poll.c
+++ b/tests/test-poll.c
@@ -362,7 +362,7 @@ test_pipe (void)
   test_pair (fd[0], fd[1]);
   close (fd[0]);
   int revents = poll1_wait (fd[1], POLLIN | POLLOUT);
-#if !defined _AIX
+#if !(defined _AIX || (defined _WIN32 && !defined __CYGWIN__))
   if ((revents & (POLLHUP | POLLERR)) == 0)
     failed ("expecting POLLHUP after shutdown");
 #else