[WIN32] 'uv_shutdown' on 'uv_pipe_t' also closes its reading side.

[Renato Maia]

In libuv v1.x (963ecc82) in Windows 10, I noticed that if I
'uv_shutdown' a 'uv_pipe_t' being read, it will cause its 'uv_read_cb'
to be called, and without calling 'uv_alloc_cb' first. Is this
expected?

I was surprised because it is not what happens in Linux, nor in
Windows if we use a 'uv_tcp_t' instead of a `uv_pipe`, which keeps
being read even after shutdown, as stated in the docs: "Shutdown the
outgoing (write) side of a duplex stream."

Finally, my code didn't expect to have 'uv_read_cb' called without
first calling the 'uv_alloc_cb', even though it will just report an
error (UV_EOF?) and therefore the buffer allocation is not necessary.
Since this seems to only happen in very rare cases
(win32+pipe+shutdown) I just wanted to check here if it was actually
expected.

I attached a small example to reproduce this scenario The output for
Linux is below, and only the server reading side is ended:

```
libuv_pipeshutdown.c:91:main(err >= 0)
libuv_pipeshutdown.c:94:main(err >= 0)
libuv_pipeshutdown.c:97:main(err >= 0)
libuv_pipeshutdown.c:99:main(err >= 0)
libuv_pipeshutdown.c:103:main(err >= 0)
libuv_pipeshutdown.c:32:on_server_accept(server_stream)
libuv_pipeshutdown.c:33:on_server_accept(err >= 0)
libuv_pipeshutdown.c:36:on_server_accept(err >= 0)
libuv_pipeshutdown.c:39:on_server_accept(err >= 0)
libuv_pipeshutdown.c:41:on_server_accept(err >= 0)
libuv_pipeshutdown.c:69:on_client_connect(shutdown_req)
libuv_pipeshutdown.c:70:on_client_connect(err >= 0)
libuv_pipeshutdown.c:72:on_client_connect(err >= 0)
libuv_pipeshutdown.c:60:on_client_shutdown(err >= 0)
libuv_pipeshutdown.c:62:on_client_shutdown(err >= 0)
libuv_pipeshutdown.c:22:on_server_alloc(handle->data == NULL)
libuv_pipeshutdown.c:15:on_server_read(stream->data == server_buffer)
libuv_pipeshutdown.c:17:on_server_read(nread == UV_EOF)
```

The ouput on Windows 10 is:

```
libuv_pipeshutdown.c:91:main(err >= 0)
libuv_pipeshutdown.c:94:main(err >= 0)
libuv_pipeshutdown.c:97:main(err >= 0)
libuv_pipeshutdown.c:99:main(err >= 0)
libuv_pipeshutdown.c:103:main(err >= 0)
libuv_pipeshutdown.c:69:on_client_connect(shutdown_req)
libuv_pipeshutdown.c:70:on_client_connect(err >= 0)
libuv_pipeshutdown.c:72:on_client_connect(err >= 0)
libuv_pipeshutdown.c:32:on_server_accept(server_stream)
libuv_pipeshutdown.c:33:on_server_accept(err >= 0)
libuv_pipeshutdown.c:36:on_server_accept(err >= 0)
libuv_pipeshutdown.c:39:on_server_accept(err >= 0)
libuv_pipeshutdown.c:41:on_server_accept(err >= 0)
libuv_pipeshutdown.c:60:on_client_shutdown(err >= 0)
libuv_pipeshutdown.c:62:on_client_shutdown(err >= 0)
libuv_pipeshutdown.c:46:on_client_read(stream->data == client_buffer)
Assertion failed: stream->data == client_buffer, file
libuv_pipeshutdown.c, line 46
```

Thanks in advance.

--
Renato Maia