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/Background.php

@@ -0,0 +1,111 @@
+<?php
+
+/**
+ * Validates shorthand CSS property background.
+ * @warning Does not support url tokens that have internal spaces.
+ */
+class HTMLPurifier_AttrDef_CSS_Background extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * Local copy of component validators.
+     * @type HTMLPurifier_AttrDef[]
+     * @note See HTMLPurifier_AttrDef_Font::$info for a similar impl.
+     */
+    protected $info;
+
+    /**
+     * @param HTMLPurifier_Config $config
+     */
+    public function __construct($config)
+    {
+        $def = $config->getCSSDefinition();
+        $this->info['background-color'] = $def->info['background-color'];
+        $this->info['background-image'] = $def->info['background-image'];
+        $this->info['background-repeat'] = $def->info['background-repeat'];
+        $this->info['background-attachment'] = $def->info['background-attachment'];
+        $this->info['background-position'] = $def->info['background-position'];
+    }
+
+    /**
+     * @param string $string
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($string, $config, $context)
+    {
+        // regular pre-processing
+        $string = $this->parseCDATA($string);
+        if ($string === '') {
+            return false;
+        }
+
+        // munge rgb() decl if necessary
+        $string = $this->mungeRgb($string);
+
+        // assumes URI doesn't have spaces in it
+        $bits = explode(' ', $string); // bits to process
+
+        $caught = array();
+        $caught['color'] = false;
+        $caught['image'] = false;
+        $caught['repeat'] = false;
+        $caught['attachment'] = false;
+        $caught['position'] = false;
+
+        $i = 0; // number of catches
+
+        foreach ($bits as $bit) {
+            if ($bit === '') {
+                continue;
+            }
+            foreach ($caught as $key => $status) {
+                if ($key != 'position') {
+                    if ($status !== false) {
+                        continue;
+                    }
+                    $r = $this->info['background-' . $key]->validate($bit, $config, $context);
+                } else {
+                    $r = $bit;
+                }
+                if ($r === false) {
+                    continue;
+                }
+                if ($key == 'position') {
+                    if ($caught[$key] === false) {
+                        $caught[$key] = '';
+                    }
+                    $caught[$key] .= $r . ' ';
+                } else {
+                    $caught[$key] = $r;
+                }
+                $i++;
+                break;
+            }
+        }
+
+        if (!$i) {
+            return false;
+        }
+        if ($caught['position'] !== false) {
+            $caught['position'] = $this->info['background-position']->
+                validate($caught['position'], $config, $context);
+        }
+
+        $ret = array();
+        foreach ($caught as $value) {
+            if ($value === false) {
+                continue;
+            }
+            $ret[] = $value;
+        }
+
+        if (empty($ret)) {
+            return false;
+        }
+        return implode(' ', $ret);
+    }
+}
+
+// vim: et sw=4 sts=4