const the member of the function call table

src/vmod_blobcode.c

@@ -58,10 +58,10 @@ struct vmod_blobcode_blob {
 		.encode	= hex_encode
 
 static const struct vmod_blobcode_fptr {
-	len_f		*decode_l;
-	decode_f	*decode;
-	len_f		*encode_l;
-	encode_f	*encode;
+	len_f		*const decode_l;
+	decode_f	*const decode;
+	len_f		*const encode_l;
+	encode_f	*const encode;
 } func[__MAX_ENCODING] = {
 	[_INVALID] = {
 		/* make implicit null init explicit for clarity */