windows: Provide shutdown(2) operation aliases mapping to those on Windows

src/libstrongswan/utils/windows.h

@@ -280,6 +280,13 @@ char* getpass(const char *prompt);
 #define ECONNRESET ENXIO
 #endif
 
+/**
+ * shutdown(2) "how"-aliases, to use Unix variant on Windows
+ */
+#define SHUT_RD SD_RECEIVE
+#define SHUT_WR SD_SEND
+#define SHUT_RDWR SD_BOTH
+
 /**
  * close(2) working for file handles and Winsock sockets
  */