Make IPSet actually support IPs, and fix protocol errors for newer kernels

[eh-steve]

Fixes #609

Added support for IPSets based on IP rather than just MAC address.

With the release of IPSet v7, the protocol response for PROTOCOL_MIN is now potentially more relevant, so the IpsetProtocol() function has been updated to return this too.

I'd like to improve the protocol testing of all functions this area to ensure protocol parity with the userland ipset binary at some point (I built a debug version of http://git.netfilter.org/ipset/ using -DIPSET_DEBUG and this patch:

Index: lib/debug.c
===================================================================
diff --git a/lib/debug.c b/lib/debug.c
--- a/lib/debug.c	(revision 258b4c0e7fc5e3365a113d6d80c7d6770e55cc4a)
+++ b/lib/debug.c	(date 1614930673366)
@@ -292,6 +292,12 @@
 			;
 		}
 		cmd = ipset_get_nlmsg_type(nlh);
+                fprintf(stderr, "Message payload: \n");
+                for (int i = 0; i < len; i++) {
+                  fprintf(stderr, "%02X", ((uint8_t*)buffer)[i]);
+                }
+
+                fprintf(stderr, "\n");
 		fprintf(stderr, "Message header: %s cmd  %s (%d)\n"
 				"\tlen %d\n"
 				"\tflag %s\n"

which prints out the serialised payloads being sent, but this package will need some refactoring to make the request generation independent of the request execution - I might put that into a separate PR

[eh-steve]

@aboch @corny @vishvananda

I'd be happy to address any comments you might have

https://travis-ci.org/github/vishvananda/netlink/builds/761936947

[aboch]

LGTM