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/Context.php

@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * Registry object that contains information about the current context.
+ * @warning Is a bit buggy when variables are set to null: it thinks
+ *          they don't exist! So use false instead, please.
+ * @note Since the variables Context deals with may not be objects,
+ *       references are very important here! Do not remove!
+ */
+class HTMLPurifier_Context
+{
+
+    /**
+     * Private array that stores the references.
+     * @type array
+     */
+    private $_storage = array();
+
+    /**
+     * Registers a variable into the context.
+     * @param string $name String name
+     * @param mixed $ref Reference to variable to be registered
+     */
+    public function register($name, &$ref)
+    {
+        if (array_key_exists($name, $this->_storage)) {
+            trigger_error(
+                "Name $name produces collision, cannot re-register",
+                E_USER_ERROR
+            );
+            return;
+        }
+        $this->_storage[$name] =& $ref;
+    }
+
+    /**
+     * Retrieves a variable reference from the context.
+     * @param string $name String name
+     * @param bool $ignore_error Boolean whether or not to ignore error
+     * @return mixed
+     */
+    public function &get($name, $ignore_error = false)
+    {
+        if (!array_key_exists($name, $this->_storage)) {
+            if (!$ignore_error) {
+                trigger_error(
+                    "Attempted to retrieve non-existent variable $name",
+                    E_USER_ERROR
+                );
+            }
+            $var = null; // so we can return by reference
+            return $var;
+        }
+        return $this->_storage[$name];
+    }
+
+    /**
+     * Destroys a variable in the context.
+     * @param string $name String name
+     */
+    public function destroy($name)
+    {
+        if (!array_key_exists($name, $this->_storage)) {
+            trigger_error(
+                "Attempted to destroy non-existent variable $name",
+                E_USER_ERROR
+            );
+            return;
+        }
+        unset($this->_storage[$name]);
+    }
+
+    /**
+     * Checks whether or not the variable exists.
+     * @param string $name String name
+     * @return bool
+     */
+    public function exists($name)
+    {
+        return array_key_exists($name, $this->_storage);
+    }
+
+    /**
+     * Loads a series of variables from an associative array
+     * @param array $context_array Assoc array of variables to load
+     */
+    public function loadArray($context_array)
+    {
+        foreach ($context_array as $key => $discard) {
+            $this->register($key, $context_array[$key]);
+        }
+    }
+}
+
+// vim: et sw=4 sts=4