XeLaTeX oldstyle figures search/copy

Question

Possible Duplicate:
Small-caps, old-style numbers, and some ligatures produce odd symbols in PDF copy text?

How can I make XeLaTeX produce PDFs that can be searched/copied? In particular, oldstyle figures don't work for the OpenType fonts I've tested. This my MWE:

\RequirePackage{cmap}
\documentclass{article}

%\input{glyphtounicode} % gives me an error
%\pdfgentounicode=1  % gives me an error

\usepackage{xltxtra}

\defaultfontfeatures{Ligatures=TeX, Scale=MatchLowercase}
\setmainfont[Ligatures=Common,
  Numbers=OldStyle,
  ]{Adobe Garamond Pro}

\begin{document}
Testing 12345678910\\
\textsc{Testing 12345678910}
\end{document}

As you see, I've included the cmap package, as well as glyphtounicode, as most answers in this forum recommend. However, when inputing glyphtounicode, with or without the \pdfgentounicode=1 command, produces the following error:

! Undefined control sequence.
l.19 \pdfglyphtounicode
                       {A}{0041}