string-list: mark unused callback parameters

String-lists may be used with callbacks for clearing or iteration. These
callbacks need to conform to a particular interface, even though not
every callback needs all of its parameters. Mark the unused ones to make
-Wunused-parameter happy.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reflog-walk.c

@@ -55,7 +55,7 @@ static void free_complete_reflog(struct complete_reflogs *array)
 	free(array);
 }
 
-static void complete_reflogs_clear(void *util, const char *str)
+static void complete_reflogs_clear(void *util, const char *str UNUSED)
 {
 	struct complete_reflogs *array = util;
 	free_complete_reflog(array);