Replace existing autoloader with Composer-supplied

- Move Friendica namespace to `src`
- Move required `ezyang/htmlpurifier` to vendor
- Remove existing static autoloader
- Change boot.php reference to the autoloader

vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrDef/HTML/ID.php

@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * Validates the HTML attribute ID.
+ * @warning Even though this is the id processor, it
+ *          will ignore the directive Attr:IDBlacklist, since it will only
+ *          go according to the ID accumulator. Since the accumulator is
+ *          automatically generated, it will have already absorbed the
+ *          blacklist. If you're hacking around, make sure you use load()!
+ */
+
+class HTMLPurifier_AttrDef_HTML_ID extends HTMLPurifier_AttrDef
+{
+
+    // selector is NOT a valid thing to use for IDREFs, because IDREFs
+    // *must* target IDs that exist, whereas selector #ids do not.
+
+    /**
+     * Determines whether or not we're validating an ID in a CSS
+     * selector context.
+     * @type bool
+     */
+    protected $selector;
+
+    /**
+     * @param bool $selector
+     */
+    public function __construct($selector = false)
+    {
+        $this->selector = $selector;
+    }
+
+    /**
+     * @param string $id
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($id, $config, $context)
+    {
+        if (!$this->selector && !$config->get('Attr.EnableID')) {
+            return false;
+        }
+
+        $id = trim($id); // trim it first
+
+        if ($id === '') {
+            return false;
+        }
+
+        $prefix = $config->get('Attr.IDPrefix');
+        if ($prefix !== '') {
+            $prefix .= $config->get('Attr.IDPrefixLocal');
+            // prevent re-appending the prefix
+            if (strpos($id, $prefix) !== 0) {
+                $id = $prefix . $id;
+            }
+        } elseif ($config->get('Attr.IDPrefixLocal') !== '') {
+            trigger_error(
+                '%Attr.IDPrefixLocal cannot be used unless ' .
+                '%Attr.IDPrefix is set',
+                E_USER_WARNING
+            );
+        }
+
+        if (!$this->selector) {
+            $id_accumulator =& $context->get('IDAccumulator');
+            if (isset($id_accumulator->ids[$id])) {
+                return false;
+            }
+        }
+
+        // we purposely avoid using regex, hopefully this is faster
+
+        if (ctype_alpha($id)) {
+            $result = true;
+        } else {
+            if (!ctype_alpha(@$id[0])) {
+                return false;
+            }
+            // primitive style of regexps, I suppose
+            $trim = trim(
+                $id,
+                'A..Za..z0..9:-._'
+            );
+            $result = ($trim === '');
+        }
+
+        $regexp = $config->get('Attr.IDBlacklistRegexp');
+        if ($regexp && preg_match($regexp, $id)) {
+            return false;
+        }
+
+        if (!$this->selector && $result) {
+            $id_accumulator->add($id);
+        }
+
+        // if no change was made to the ID, return the result
+        // else, return the new id if stripping whitespace made it
+        //     valid, or return false.
+        return $result ? $id : false;
+    }
+}
+
+// vim: et sw=4 sts=4