all: consistent syntax use in struct option

Try to inhibit copypasting old stuff.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/extensions/libip6t_icmp6.c b/extensions/libip6t_icmp6.c
index fb321b3..b8a6ec9 100644
--- a/extensions/libip6t_icmp6.c
+++ b/extensions/libip6t_icmp6.c
@@ -1,4 +1,5 @@
 /* Shared library add-on to ip6tables to add ICMP support. */
+#include <stdbool.h>
 #include <stdio.h>
 #include <netdb.h>
 #include <string.h>
@@ -84,8 +85,8 @@
 }
 
 static const struct option icmp6_opts[] = {
-	{ "icmpv6-type", 1, NULL, '1' },
-	{ .name = NULL }
+	{.name = "icmpv6-type", .has_arg = true, .val = '1'},
+	XT_GETOPT_TABLEEND,
 };
 
 static void