too long timeouts in win32 vlc_poll

When vlc_poll is called with timeout of i.e. 5000ms it may happen that the
waiting time might be as long as 2500s ! Probably poll should be called with
the 50ms timeout as many times until the original provided timeout has been
reached.
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

include/vlc_threads.h

@@ -392,7 +392,7 @@ static inline int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
 
     while (timeout > 50)
     {
-        int val = poll (fds, nfds, timeout);
+        int val = poll (fds, nfds, 50);
         if (val != 0)
             return val;
         timeout -= 50;