windows: Provide a sched_yield() implementation

src/libstrongswan/utils/utils.h

@@ -36,6 +36,7 @@
 # include <sys/socket.h>
 # include <netdb.h>
 # include <netinet/in.h>
+# include <sched.h>
 #endif
 
 /**

src/libstrongswan/utils/windows.h

@@ -67,6 +67,15 @@ static inline void srandom(unsigned int seed)
 	srand(seed);
 }
 
+/**
+ * Replacement of sched_yield(2) from <sched.h>
+ */
+static inline int sched_yield(void)
+{
+	Sleep(0);
+	return 0;
+}
+
 /**
  * strdup(3), the Windows variant can't free(strdup("")) and others
  */