windows: Add a sleep function acting as cancellation point

src/libstrongswan/utils/windows.h

@@ -76,6 +76,15 @@ static inline int sched_yield(void)
 	return 0;
 }
 
+/**
+ * Replacement of sleep(3), cancellable by thread_cancel()
+ */
+static inline int sleep(unsigned int seconds)
+{
+	SleepEx(seconds * 1000, TRUE);
+	return 0;
+}
+
 /**
  * strdup(3), the Windows variant can't free(strdup("")) and others
  */