Fix compilation of os_support.c for MinGW with --disable-network

Patch by Tom Harper <d.thomas.harper <at> gmail.com>

Originally committed as revision 11200 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/os_support.c

@@ -25,6 +25,7 @@
 #include <fcntl.h>
 #include "os_support.h"
 
+#ifdef CONFIG_NETWORK
 #ifndef HAVE_SYS_POLL_H
 #ifdef HAVE_WINSOCK2_H
 #include <winsock2.h>
@@ -33,7 +34,6 @@
 #endif
 #endif
 
-#ifdef CONFIG_NETWORK
 #include "network.h"
 
 #if !defined(HAVE_INET_ATON)