Setup ErrorCollector to maintain new error format, and output that HTML.

Also changed:
    - DirectLex keeps track of column numbers in context
    - New class HTMLPurifier_ErrorStruct

Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>

library/HTMLPurifier/ErrorStruct.php

@@ -0,0 +1,58 @@
+<?php
+
+/**
+ * Records errors for particular segments of an HTML document such as tokens,
+ * attributes or CSS properties. They can contain error structs (which apply
+ * to components of what they represent), but their main purpose is to hold
+ * errors applying to whatever struct is being used.
+ */
+class HTMLPurifier_ErrorStruct
+{
+    
+    /**
+     * Possible values for $children first-key. Note that top-level structures
+     * are automatically token-level.
+     */
+    const TOKEN     = 0;
+    const ATTR      = 1;
+    const CSSPROP   = 2;
+    
+    /**
+     * Type of this struct.
+     */
+    public $type;
+    
+    /**
+     * Value of the struct we are recording errors for. There are various
+     * values for this:
+     *  - TOKEN: Instance of HTMLPurifier_Token
+     *  - ATTR: array('attr-name', 'value')
+     *  - CSSPROP: array('prop-name', 'value')
+     */
+    public $value;
+    
+    /**
+     * Errors registered for this structure.
+     */
+    public $errors = array();
+    
+    /**
+     * Child ErrorStructs that are from this structure. For example, a TOKEN
+     * ErrorStruct would contain ATTR ErrorStructs. This is a multi-dimensional
+     * array in structure: [TYPE]['identifier']
+     */
+    public $children = array();
+    
+    public function getChild($type, $id) {
+        if (!isset($this->children[$type][$id])) {
+            $this->children[$type][$id] = new HTMLPurifier_ErrorStruct();
+            $this->children[$type][$id]->type = $type;
+        }
+        return $this->children[$type][$id];
+    }
+    
+    public function addError($severity, $message) {
+        $this->errors[] = array($severity, $message);
+    }
+    
+}