libxtables: prefix/order - move check_inverse to xtables.c

This also adds a warning that intrapositional negation support
is deprecated.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/extensions/libip6t_icmp6.c b/extensions/libip6t_icmp6.c
index 401c278..5af9b02 100644
--- a/extensions/libip6t_icmp6.c
+++ b/extensions/libip6t_icmp6.c
@@ -157,7 +157,7 @@
 		if (*flags == 1)
 			exit_error(PARAMETER_PROBLEM,
 				   "icmpv6 match: only use --icmpv6-type once!");
-		check_inverse(optarg, &invert, &optind, 0);
+		xtables_check_inverse(optarg, &invert, &optind, 0);
 		parse_icmpv6(argv[optind-1], &icmpv6info->type, 
 			     icmpv6info->code);
 		if (invert)