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/Input.php

@@ -0,0 +1,56 @@
+<?php
+
+/**
+ * Performs miscellaneous cross attribute validation and filtering for
+ * input elements. This is meant to be a post-transform.
+ */
+class HTMLPurifier_AttrTransform_Input extends HTMLPurifier_AttrTransform
+{
+    /**
+     * @type HTMLPurifier_AttrDef_HTML_Pixels
+     */
+    protected $pixels;
+
+    public function __construct()
+    {
+        $this->pixels = new HTMLPurifier_AttrDef_HTML_Pixels();
+    }
+
+    /**
+     * @param array $attr
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return array
+     */
+    public function transform($attr, $config, $context)
+    {
+        if (!isset($attr['type'])) {
+            $t = 'text';
+        } else {
+            $t = strtolower($attr['type']);
+        }
+        if (isset($attr['checked']) && $t !== 'radio' && $t !== 'checkbox') {
+            unset($attr['checked']);
+        }
+        if (isset($attr['maxlength']) && $t !== 'text' && $t !== 'password') {
+            unset($attr['maxlength']);
+        }
+        if (isset($attr['size']) && $t !== 'text' && $t !== 'password') {
+            $result = $this->pixels->validate($attr['size'], $config, $context);
+            if ($result === false) {
+                unset($attr['size']);
+            } else {
+                $attr['size'] = $result;
+            }
+        }
+        if (isset($attr['src']) && $t !== 'image') {
+            unset($attr['src']);
+        }
+        if (!isset($attr['value']) && ($t === 'radio' || $t === 'checkbox')) {
+            $attr['value'] = '';
+        }
+        return $attr;
+    }
+}
+
+// vim: et sw=4 sts=4