Make the option structures const.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
diff --git a/extensions/libipt_REJECT.c b/extensions/libipt_REJECT.c
index 4e083f3..8aba561 100644
--- a/extensions/libipt_REJECT.c
+++ b/extensions/libipt_REJECT.c
@@ -80,7 +80,7 @@
 	printf("(*) See man page or read the INCOMPATIBILITES file for compatibility issues.\n");
 }
 
-static struct option opts[] = {
+static const struct option opts[] = {
 	{ "reject-with", 1, 0, '1' },
 	{ 0 }
 };