[ticket/12224] Add template wrapper method to assign block arrays

Add one more wrapper template method for the function assign_block_vars() which
takes a 2-dimensional array as a parameter
and calls assign_block_vars() in a loop to assign the whole block loop at once.
This can make the core a little bit more expendable from the point of
developing extensions as it allows to pass the data to events before
it's being assigned to template.

PHPBB3-12224

phpBB/phpbb/template/template.php

@@ -131,6 +131,14 @@ interface template
 	*/
 	public function assign_block_vars($blockname, array $vararray);
 
+	/**
+	* Assign key variable pairs from an array to a whole specified block loop
+	* @param string $blockname Name of block to assign $block_vars_array to
+	* @param array $block_vars_array An array of hashes of variable name => value pairs
+	* @return \phpbb\template\template $this
+	*/
+	public function assign_block_vars_array($blockname, array $block_vars_array);
+
 	/**
 	* Change already assigned key variable pair (one-dimensional - single loop entry)
 	*