src: use NFPROTO_ constants

Resync netfilter.h from the latest kernel and make use of the new
NFPROTO_ constants that have been introduced.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/extensions/libipt_TTL.c b/extensions/libipt_TTL.c
index 9c22ba3..7939dac 100644
--- a/extensions/libipt_TTL.c
+++ b/extensions/libipt_TTL.c
@@ -141,7 +141,7 @@
 static struct xtables_target ttl_tg_reg = {
 	.name		= "TTL",
 	.version	= XTABLES_VERSION,
-	.family		= PF_INET,
+	.family		= NFPROTO_IPV4,
 	.size		= XT_ALIGN(sizeof(struct ipt_TTL_info)),
 	.userspacesize	= XT_ALIGN(sizeof(struct ipt_TTL_info)),
 	.help		= TTL_help,