[ticket/13680] Updated quote notifications

Added get_quote_authors() to text_formatter.utils service to retrieve
the names used in first-level quotes

PHPBB3-13680

phpBB/phpbb/textformatter/utils_interface.php

@@ -28,6 +28,14 @@ interface utils_interface
 	*/
 	public function clean_formatting($text);
 
+	/**
+	* Get a list of quote authors, limited to the first level of quotes
+	*
+	* @param  string   $text Parsed text
+	* @return string[]       List of authors
+	*/
+	public function get_quote_authors($text);
+
 	/**
 	* Remove given BBCode and its content, at given nesting depth
 	*