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/EnumToCSS.php

@@ -0,0 +1,68 @@
+<?php
+
+/**
+ * Generic pre-transform that converts an attribute with a fixed number of
+ * values (enumerated) to CSS.
+ */
+class HTMLPurifier_AttrTransform_EnumToCSS extends HTMLPurifier_AttrTransform
+{
+    /**
+     * Name of attribute to transform from.
+     * @type string
+     */
+    protected $attr;
+
+    /**
+     * Lookup array of attribute values to CSS.
+     * @type array
+     */
+    protected $enumToCSS = array();
+
+    /**
+     * Case sensitivity of the matching.
+     * @type bool
+     * @warning Currently can only be guaranteed to work with ASCII
+     *          values.
+     */
+    protected $caseSensitive = false;
+
+    /**
+     * @param string $attr Attribute name to transform from
+     * @param array $enum_to_css Lookup array of attribute values to CSS
+     * @param bool $case_sensitive Case sensitivity indicator, default false
+     */
+    public function __construct($attr, $enum_to_css, $case_sensitive = false)
+    {
+        $this->attr = $attr;
+        $this->enumToCSS = $enum_to_css;
+        $this->caseSensitive = (bool)$case_sensitive;
+    }
+
+    /**
+     * @param array $attr
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return array
+     */
+    public function transform($attr, $config, $context)
+    {
+        if (!isset($attr[$this->attr])) {
+            return $attr;
+        }
+
+        $value = trim($attr[$this->attr]);
+        unset($attr[$this->attr]);
+
+        if (!$this->caseSensitive) {
+            $value = strtolower($value);
+        }
+
+        if (!isset($this->enumToCSS[$value])) {
+            return $attr;
+        }
+        $this->prependCSS($attr, $this->enumToCSS[$value]);
+        return $attr;
+    }
+}
+
+// vim: et sw=4 sts=4