glib: fix g_poll early timeout on windows

glib: fix g_poll early timeout on windows

g_poll has a problem on Windows when using
timeouts < 10ms, in glib/gpoll.c:

/* If not, and we have a significant timeout, poll again with
 * timeout then. Note that this will return indication for only
 * one event, or only for messages. We ignore timeouts less than
 * ten milliseconds as they are mostly pointless on Windows, the
 * MsgWaitForMultipleObjectsEx() call will timeout right away
 * anyway.
 */
if (retval == 0 && (timeout == INFINITE || timeout >= 10))
  retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, timeout);

so whenever g_poll is called with timeout < 10ms it does
a quick poll instead of wait, this causes significant performance
degradation of QEMU, thus we should use WaitForMultipleObjectsEx
directly

Signed-off-by: Stanislav Vorobiov <s.vorobiov@samsung.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>