Clang16 will not allow implicit function declarations by default.
This patch overhauls the source to make it build with clang16 defaults.

This patch was sent upstream via mail.
Bug: https://bugs.gentoo.org/874012

# Pascal Jäger <pascal.jaeger@leimstift.de> (2022-11-23)

--- a/http.c
+++ b/http.c
@@ -2,6 +2,7 @@
 
 #include <config.h>
 
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
--- a/util.c
+++ b/util.c
@@ -33,8 +33,11 @@
 #include <errno.h>
 #include <time.h>
 #include <libgen.h>
-#include "url.h"
+#include "ftp.h"
+#include "gopher.h"
+#include "http.h"
 #include "options.h"
+#include "url.h"
 
 
 char output_buf[BUFSIZ];