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/Injector/RemoveEmpty.php

@@ -0,0 +1,106 @@
+<?php
+
+class HTMLPurifier_Injector_RemoveEmpty extends HTMLPurifier_Injector
+{
+    /**
+     * @type HTMLPurifier_Context
+     */
+    private $context;
+
+    /**
+     * @type HTMLPurifier_Config
+     */
+    private $config;
+
+    /**
+     * @type HTMLPurifier_AttrValidator
+     */
+    private $attrValidator;
+
+    /**
+     * @type bool
+     */
+    private $removeNbsp;
+
+    /**
+     * @type bool
+     */
+    private $removeNbspExceptions;
+
+    /**
+     * Cached contents of %AutoFormat.RemoveEmpty.Predicate
+     * @type array
+     */
+    private $exclude;
+
+    /**
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return void
+     */
+    public function prepare($config, $context)
+    {
+        parent::prepare($config, $context);
+        $this->config = $config;
+        $this->context = $context;
+        $this->removeNbsp = $config->get('AutoFormat.RemoveEmpty.RemoveNbsp');
+        $this->removeNbspExceptions = $config->get('AutoFormat.RemoveEmpty.RemoveNbsp.Exceptions');
+        $this->exclude = $config->get('AutoFormat.RemoveEmpty.Predicate');
+        $this->attrValidator = new HTMLPurifier_AttrValidator();
+    }
+
+    /**
+     * @param HTMLPurifier_Token $token
+     */
+    public function handleElement(&$token)
+    {
+        if (!$token instanceof HTMLPurifier_Token_Start) {
+            return;
+        }
+        $next = false;
+        $deleted = 1; // the current tag
+        for ($i = count($this->inputZipper->back) - 1; $i >= 0; $i--, $deleted++) {
+            $next = $this->inputZipper->back[$i];
+            if ($next instanceof HTMLPurifier_Token_Text) {
+                if ($next->is_whitespace) {
+                    continue;
+                }
+                if ($this->removeNbsp && !isset($this->removeNbspExceptions[$token->name])) {
+                    $plain = str_replace("\xC2\xA0", "", $next->data);
+                    $isWsOrNbsp = $plain === '' || ctype_space($plain);
+                    if ($isWsOrNbsp) {
+                        continue;
+                    }
+                }
+            }
+            break;
+        }
+        if (!$next || ($next instanceof HTMLPurifier_Token_End && $next->name == $token->name)) {
+            $this->attrValidator->validateToken($token, $this->config, $this->context);
+            $token->armor['ValidateAttributes'] = true;
+            if (isset($this->exclude[$token->name])) {
+                $r = true;
+                foreach ($this->exclude[$token->name] as $elem) {
+                    if (!isset($token->attr[$elem])) $r = false;
+                }
+                if ($r) return;
+            }
+            if (isset($token->attr['id']) || isset($token->attr['name'])) {
+                return;
+            }
+            $token = $deleted + 1;
+            for ($b = 0, $c = count($this->inputZipper->front); $b < $c; $b++) {
+                $prev = $this->inputZipper->front[$b];
+                if ($prev instanceof HTMLPurifier_Token_Text && $prev->is_whitespace) {
+                    continue;
+                }
+                break;
+            }
+            // This is safe because we removed the token that triggered this.
+            $this->rewindOffset($b+$deleted);
+            return;
+        }
+    }
+}
+
+// vim: et sw=4 sts=4