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/Lang.php

@@ -0,0 +1,86 @@
+<?php
+
+/**
+ * Validates the HTML attribute lang, effectively a language code.
+ * @note Built according to RFC 3066, which obsoleted RFC 1766
+ */
+class HTMLPurifier_AttrDef_Lang extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * @param string $string
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($string, $config, $context)
+    {
+        $string = trim($string);
+        if (!$string) {
+            return false;
+        }
+
+        $subtags = explode('-', $string);
+        $num_subtags = count($subtags);
+
+        if ($num_subtags == 0) { // sanity check
+            return false;
+        }
+
+        // process primary subtag : $subtags[0]
+        $length = strlen($subtags[0]);
+        switch ($length) {
+            case 0:
+                return false;
+            case 1:
+                if (!($subtags[0] == 'x' || $subtags[0] == 'i')) {
+                    return false;
+                }
+                break;
+            case 2:
+            case 3:
+                if (!ctype_alpha($subtags[0])) {
+                    return false;
+                } elseif (!ctype_lower($subtags[0])) {
+                    $subtags[0] = strtolower($subtags[0]);
+                }
+                break;
+            default:
+                return false;
+        }
+
+        $new_string = $subtags[0];
+        if ($num_subtags == 1) {
+            return $new_string;
+        }
+
+        // process second subtag : $subtags[1]
+        $length = strlen($subtags[1]);
+        if ($length == 0 || ($length == 1 && $subtags[1] != 'x') || $length > 8 || !ctype_alnum($subtags[1])) {
+            return $new_string;
+        }
+        if (!ctype_lower($subtags[1])) {
+            $subtags[1] = strtolower($subtags[1]);
+        }
+
+        $new_string .= '-' . $subtags[1];
+        if ($num_subtags == 2) {
+            return $new_string;
+        }
+
+        // process all other subtags, index 2 and up
+        for ($i = 2; $i < $num_subtags; $i++) {
+            $length = strlen($subtags[$i]);
+            if ($length == 0 || $length > 8 || !ctype_alnum($subtags[$i])) {
+                return $new_string;
+            }
+            if (!ctype_lower($subtags[$i])) {
+                $subtags[$i] = strtolower($subtags[$i]);
+            }
+            $new_string .= '-' . $subtags[$i];
+        }
+        return $new_string;
+    }
+}
+
+// vim: et sw=4 sts=4