Add format argument to avoid format-security error while building.

--- a/output.c
+++ b/output.c
@@ -1864,7 +1864,7 @@
          if(pcent >= 1)
             snprintf(buffer, sizeof(buffer), _2utf8(_("%.0f%% of all requests")), pcent);
          else
-            snprintf(buffer, sizeof(buffer), _2utf8(_("less than 1%% of all requests")));
+            snprintf(buffer, sizeof(buffer), "%s", _2utf8(_("less than 1%% of all requests")));
 
          fprintf(main_fp, "<TR>\n");
          fprintf(main_fp, "   <TH BGCOLOR=\"#FFFF00\" ALIGN=LEFT COLSPAN=5>%s (%s)</TH>\n",