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/AttrTransform.php

@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * Processes an entire attribute array for corrections needing multiple values.
+ *
+ * Occasionally, a certain attribute will need to be removed and popped onto
+ * another value.  Instead of creating a complex return syntax for
+ * HTMLPurifier_AttrDef, we just pass the whole attribute array to a
+ * specialized object and have that do the special work.  That is the
+ * family of HTMLPurifier_AttrTransform.
+ *
+ * An attribute transformation can be assigned to run before or after
+ * HTMLPurifier_AttrDef validation.  See HTMLPurifier_HTMLDefinition for
+ * more details.
+ */
+
+abstract class HTMLPurifier_AttrTransform
+{
+
+    /**
+     * Abstract: makes changes to the attributes dependent on multiple values.
+     *
+     * @param array $attr Assoc array of attributes, usually from
+     *              HTMLPurifier_Token_Tag::$attr
+     * @param HTMLPurifier_Config $config Mandatory HTMLPurifier_Config object.
+     * @param HTMLPurifier_Context $context Mandatory HTMLPurifier_Context object
+     * @return array Processed attribute array.
+     */
+    abstract public function transform($attr, $config, $context);
+
+    /**
+     * Prepends CSS properties to the style attribute, creating the
+     * attribute if it doesn't exist.
+     * @param array &$attr Attribute array to process (passed by reference)
+     * @param string $css CSS to prepend
+     */
+    public function prependCSS(&$attr, $css)
+    {
+        $attr['style'] = isset($attr['style']) ? $attr['style'] : '';
+        $attr['style'] = $css . $attr['style'];
+    }
+
+    /**
+     * Retrieves and removes an attribute
+     * @param array &$attr Attribute array to process (passed by reference)
+     * @param mixed $key Key of attribute to confiscate
+     * @return mixed
+     */
+    public function confiscateAttr(&$attr, $key)
+    {
+        if (!isset($attr[$key])) {
+            return null;
+        }
+        $value = $attr[$key];
+        unset($attr[$key]);
+        return $value;
+    }
+}
+
+// vim: et sw=4 sts=4