string_list: Fix argument order for string_list_insert

Update the definition and callers of string_list_insert to use the
string_list as the first argument.  This helps make the string_list
API easier to use by being more consistent.

Signed-off-by: Julian Phillips <julian@quantumfyre.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/reflog-walk.c b/reflog-walk.c
index caba4f7..f125f37 100644
--- a/reflog-walk.c
+++ b/reflog-walk.c
@@ -190,7 +190,7 @@
 		}
 		if (!reflogs || reflogs->nr == 0)
 			return -1;
-		string_list_insert(branch, &info->complete_reflogs)->util
+		string_list_insert(&info->complete_reflogs, branch)->util
 			= reflogs;
 	}