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/Enum.php

@@ -0,0 +1,73 @@
+<?php
+
+// Enum = Enumerated
+/**
+ * Validates a keyword against a list of valid values.
+ * @warning The case-insensitive compare of this function uses PHP's
+ *          built-in strtolower and ctype_lower functions, which may
+ *          cause problems with international comparisons
+ */
+class HTMLPurifier_AttrDef_Enum extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * Lookup table of valid values.
+     * @type array
+     * @todo Make protected
+     */
+    public $valid_values = array();
+
+    /**
+     * Bool indicating whether or not enumeration is case sensitive.
+     * @note In general this is always case insensitive.
+     */
+    protected $case_sensitive = false; // values according to W3C spec
+
+    /**
+     * @param array $valid_values List of valid values
+     * @param bool $case_sensitive Whether or not case sensitive
+     */
+    public function __construct($valid_values = array(), $case_sensitive = false)
+    {
+        $this->valid_values = array_flip($valid_values);
+        $this->case_sensitive = $case_sensitive;
+    }
+
+    /**
+     * @param string $string
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($string, $config, $context)
+    {
+        $string = trim($string);
+        if (!$this->case_sensitive) {
+            // we may want to do full case-insensitive libraries
+            $string = ctype_lower($string) ? $string : strtolower($string);
+        }
+        $result = isset($this->valid_values[$string]);
+
+        return $result ? $string : false;
+    }
+
+    /**
+     * @param string $string In form of comma-delimited list of case-insensitive
+     *      valid values. Example: "foo,bar,baz". Prepend "s:" to make
+     *      case sensitive
+     * @return HTMLPurifier_AttrDef_Enum
+     */
+    public function make($string)
+    {
+        if (strlen($string) > 2 && $string[0] == 's' && $string[1] == ':') {
+            $string = substr($string, 2);
+            $sensitive = true;
+        } else {
+            $sensitive = false;
+        }
+        $values = explode(',', $string);
+        return new HTMLPurifier_AttrDef_Enum($values, $sensitive);
+    }
+}
+
+// vim: et sw=4 sts=4