! Undefined control sequence. l.52 \char_make_active:n {"20}% [closed]

Question

This is the XeTeX code I copied from Wikipedia, theoretically it must be working:

\documentclass[11pt]{article}
\usepackage{xltxtra}
\setmainfont[Mapping=tex-text]{Linux Libertine O}
\begin{document}
\section{Unicode support}

\subsection{English}
All human beings are born free and equal in dignity and rights.

\subsection{Íslenska}
Hver maður er borinn frjáls og jafn öðrum að virðingu og réttindum.

\subsection{Русский}  
Все люди рождаются свободными и равными в своем достоинстве и 
правах.

\subsection{Tiếng Việt}
Tất cả mọi người sinh ra đều được tự do và bình đẳng về nhân phẩm và 
quyền lợi.

\subsection{Ελληνικά} 
Ὅλοι οἱ ἄνθρωποι γεννιοῦνται ἐλεύθεροι καὶ ἴσοι στὴν ἀξιοπρέπεια 
καὶ τὰ δικαιώματα.

\section{Legacy syntax}
When he goes---``Hello World!''\\
She replies—“Hello dear!”

\section{Ligatures}
\fontspec[Ligatures={Common, Historical}]{Linux Libertine O Italic}
\fontsize{12pt}{18pt}\selectfont Questo è strano assai!

\section{Numerals}
\fontspec[Numbers={OldStyle}]{Linux Libertine O}Old style: 1234567\\
\fontspec[Numbers={Lining}]{Linux Libertine O}Lining: 1234567

\end{document}

I used TeXworks and XeLaTeX to compile, it asked me to download a bunch of packages but in the end it only gave me this error:

! Undefined control sequence.
l.52 \char_make_active:n
                    {"20}%

This LaTeX really makes me crazy, for the lack of Unicode support and every solution to get around this problem seems to be equally painful. But I have to use LaTeX for my thesis, so, so you know how to fix the damn error above or any other way to add multi-language Unicode support feature to LaTeX?

Thanks.

By the way, my thesis is about human languages, so the support for CJK (Chinese, Japanese, Korean, Thai, Vietnamese) and some Western languages are needed.