fix warnings

Author: c-cube

src/Tiny_httpd_dir.ml

@@ -1,7 +1,6 @@
 module S = Tiny_httpd_server
 module U = Tiny_httpd_util
 module Html = Tiny_httpd_html
-module Pf = Printf
 
 type dir_behavior =
   | Index | Lists | Index_or_lists | Forbidden

src/dune

@@ -3,7 +3,7 @@
   (name tiny_httpd)
   (public_name tiny_httpd)
   (libraries threads seq)
-  (flags :standard -safe-string -warn-error -a+8)
+  (flags :standard -safe-string -strict-sequence -w +a-4-40-42 -warn-error -a+8)
   (wrapped false))
 
 (rule