Revert "libipsec: Added Windows tun device support"

This reverts commit 77b91e6d0e.

src/libstrongswan/networking/tun_device.h

@@ -2,7 +2,6 @@
  * Copyright (C) 2012 Tobias Brunner
  * Copyright (C) 2012 Giuliano Grassi
  * Copyright (C) 2012 Ralf Sager
- * Copyright (C) 2020 Noel Kuntze
  *
  * Copyright (C) secunet Security Networks AG
  *
@@ -101,21 +100,12 @@ struct tun_device_t {
 	 */
 	char *(*get_name)(tun_device_t *this);
 
-#ifdef WIN32
-	/**
-	 * Get the underlying HANDLE.
-	 *
-	 * @return				file HANDLE of this tun device
-	 */
-	HANDLE (*get_handle)(tun_device_t *this);
-#else /* !WIN32 */
 	/**
 	 * Get the underlying tun file descriptor.
 	 *
 	 * @return				file descriptor of this tun device
 	 */
 	int (*get_fd)(tun_device_t *this);
-#endif
 
 	/**
 	 * Destroy a tun_device_t