Parser::FunctionsReturningStrings() doesn't check for custom DQL functions.

I defined a custom DQL FunctionNode that wasn't detected by the Parser.
Problem was in the Parser::FunctionsReturningStrings(), but I suspect the problem is more general.

Here's my (ugly) fix:

public function FunctionsReturningStrings()
{
$funcNameLower = strtolower($this->_lexer->lookahead['value']);
if (isset(self::$_STRING_FUNCTIONS[$funcNameLower]))

else $function = $this->CustomFunctionsReturningStrings();

return $function;
}

I include the custom DQL FunctionNode created.