minor fix on poll-msw.c and poll-msw.h for build against win10 sdk

moo/lib/poll-msw.c

@@ -23,10 +23,11 @@
 # pragma GCC diagnostic ignored "-Wtype-limits"
 #endif
 
-#include "poll-msw.h"
 #include <winsock2.h>
 #include <windows.h>
 
+#include "poll-msw.h"
+
 #include <sys/types.h>
 #include <time.h>
 #include <errno.h>

moo/lib/poll-msw.h

@@ -3,6 +3,7 @@
 
 #include "moo.h"
 
+#if !defined(_WIN32_WINNT) || (_WIN32_WINNT < 0x0600)
 /* Event types that can be polled for.  These bits may be set in `events'
    to indicate the interesting event types; they will appear in `revents'
    to indicate the status of the file descriptor.  */
@@ -30,9 +31,11 @@ struct pollfd
    an event to occur; if TIMEOUT is -1, block until an event occurs.
    Returns the number of file descriptors with events, zero if timed out,
    or -1 for errors.  */
+#endif
 
 typedef unsigned long nfds_t;
 
+
 #if defined(__cplusplus)
 extern "C" {
 #endif