[CORE][COMPOSER] Move extlib packages with immediate composer correspondent to composer dependencies

This adds a composer.json for all dependencies that are available

vendor/ezyang/htmlpurifier/library/HTMLPurifier/Token/Empty.php

@@ -0,0 +1,15 @@
+<?php
+
+/**
+ * Concrete empty token class.
+ */
+class HTMLPurifier_Token_Empty extends HTMLPurifier_Token_Tag
+{
+    public function toNode() {
+        $n = parent::toNode();
+        $n->empty = true;
+        return $n;
+    }
+}
+
+// vim: et sw=4 sts=4