Fix warnings and errors in samples

- Use <netipx/ipx.h> from glibc, because Linux 5.15 removes <linux/ipx.h>
- Pack whole structure instead of individual fields
- Network is 32bit value, avoid unsigned long to work on 64bit systems

Samples/ipxsend.c

@@ -2,7 +2,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
-#include <linux/ipx.h>
+#include <netipx/ipx.h>
 #include <netinet/in.h>
 #include <sys/socket.h>
 #include <errno.h>