network: Include unistd.h from network.h

This heaader is required for close() for sockets in network
code. For winsock, the equivalent function is defined in the
winsock2.h header.

This avoids having the HAVE_UNISTD_H in all files dealing with
raw sockets.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/tcp.c

@@ -20,7 +20,6 @@
  */
 #include "avformat.h"
 #include "libavutil/parseutils.h"
-#include <unistd.h>
 #include "internal.h"
 #include "network.h"
 #include "os_support.h"