Port the code to PHP 8.5.

Replace the short open tags and the removed functions (mcrypt, mysql_error,
salt-less crypt). Decode the reCAPTCHA reply as JSON, turn off mysqli
exceptions, drop stripslashes(), and default missing input values.
Fix the misplaced continue in prune_images().

index.php

@@ -1,4 +1,4 @@
-<? require_once("./session.lib.php"); ?>
+<?php require_once("./session.lib.php"); ?>
 <!DOCTYPE html>
 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
   <head>
@@ -11,7 +11,7 @@
     <script type="text/javascript" src="utilities.js"></script>
     <link rel="alternate" type="application/rss+xml" title="xxx.org.za RSS feed" href="/feed" />
   </head>
-<? 
+<?php 
   flush();
   $num_stories = 5;
   $editable    = FALSE;
@@ -21,7 +21,7 @@
 ?>
 <body>
 <div id="container">
-<? include_once("./sidebar.inc.php"); ?>
+<?php include_once("./sidebar.inc.php"); ?>
 <main id="main">
 <div id="maintext">
 
@@ -36,7 +36,7 @@ encouraged!
 </p>
 <p>You can send in an entry <a href="/publish/">here</a>; take a shufty at the <a href="about">guidelines</a>.</p>
 
-<?
+<?php
 
 echo display_stories();
 
@@ -44,9 +44,9 @@ echo display_stories();
 </div> <!-- .maintext  -->
 </main> <!-- .main      -->
 </div> <!-- .container -->
-<? include_once("./bottombar.inc.php"); ?>
+<?php include_once("./bottombar.inc.php"); ?>
 
-<? open_db('close'); ?>
+<?php open_db('close'); ?>
 
 </body>
 </html>