Add RDoc for Module.included

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@6836 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

path: root/sample/fib.pl

sub fib {
    my($n)=@_;
    if ($n<2) {
	return $n;
    }
    else {
	return fib($n-2)+fib($n-1);
    }
}

print fib(20), "\n";