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/CSS/Length.php

@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * Represents a Length as defined by CSS.
+ */
+class HTMLPurifier_AttrDef_CSS_Length extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * @type HTMLPurifier_Length|string
+     */
+    protected $min;
+
+    /**
+     * @type HTMLPurifier_Length|string
+     */
+    protected $max;
+
+    /**
+     * @param HTMLPurifier_Length|string $min Minimum length, or null for no bound. String is also acceptable.
+     * @param HTMLPurifier_Length|string $max Maximum length, or null for no bound. String is also acceptable.
+     */
+    public function __construct($min = null, $max = null)
+    {
+        $this->min = $min !== null ? HTMLPurifier_Length::make($min) : null;
+        $this->max = $max !== null ? HTMLPurifier_Length::make($max) : null;
+    }
+
+    /**
+     * @param string $string
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($string, $config, $context)
+    {
+        $string = $this->parseCDATA($string);
+
+        // Optimizations
+        if ($string === '') {
+            return false;
+        }
+        if ($string === '0') {
+            return '0';
+        }
+        if (strlen($string) === 1) {
+            return false;
+        }
+
+        $length = HTMLPurifier_Length::make($string);
+        if (!$length->isValid()) {
+            return false;
+        }
+
+        if ($this->min) {
+            $c = $length->compareTo($this->min);
+            if ($c === false) {
+                return false;
+            }
+            if ($c < 0) {
+                return false;
+            }
+        }
+        if ($this->max) {
+            $c = $length->compareTo($this->max);
+            if ($c === false) {
+                return false;
+            }
+            if ($c > 0) {
+                return false;
+            }
+        }
+        return $length->toString();
+    }
+}
+
+// vim: et sw=4 sts=4