netstat: include sys/stat.h for S_ISREG macros

newer versions of glibc (like 2.12) have cleaned up headers so you need
to include sys/stat.h explicitly for S_XXX macros

Gentoo bug 332853

netstat.c

@@ -6,7 +6,7 @@
  *              NET-3 Networking Distribution for the LINUX operating
  *              system.
  *
- * Version:     $Id: netstat.c,v 1.69 2010-03-05 15:35:02 ecki Exp $
+ * Version:     $Id: netstat.c,v 1.70 2010-08-15 16:09:31 vapier Exp $
  *
  * Authors:     Fred Baumgarten, <dc6iq@insu1.etec.uni-karlsruhe.de>
  *              Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
@@ -85,6 +85,7 @@
 #include <arpa/inet.h>
 #include <netinet/in.h>
 #include <sys/ioctl.h>
+#include <sys/stat.h>
 #include <net/if.h>
 #include <dirent.h>