- overhauled search system

- updated structure for search backend plugins
  - better result caching using ACM
  - search results no longer session restricted => link to them by copying the URL :)
  - in-topic search
  - indexing posts now uses search backend plugins
  - develop/search_fill.php working again
  - fulltext_mysql not working yet
- tiny bugfixes to ACM


git-svn-id: file:///svn/phpbb/trunk@5441 89ea8834-ac86-4346-8a33-228a782c2dd0

phpBB/includes/acm/acm_file.php

@@ -154,6 +154,11 @@ class acm
 	{
 		global $phpEx;
 
+		if (!$this->_exists($var_name))
+		{
+			return;
+		}
+
 		if ($var_name == 'sql' && !empty($table))
 		{
 			$regex = '(' . ((is_array($table)) ? implode('|', $table) : $table) . ')';