[XeTeX] change bars

[Mike Maxwell]

Is there a way with xe(la)tex to display change bars (those vertical 
lines in the margins marking text that's changed)?

The changebar package (according to the PDF documentation dated 2005) 
does not support the xdvipdfmx driver; the possible drivers include 
DVItoLN03, DVItoPS, DVIps, emtex, textures, vtex, and PDFTEX.  Using the 
default driver (DVIps) results in error msgs from xdvipdfmx, and no 
changebars:
---------------
** WARNING ** Unknown token "Resolution"
** WARNING ** Interpreting PS code failed!!! Output might be broken!!!
** WARNING ** Interpreting special command ps: (ps:) failed.
** WARNING ** >> at page="1" position="(160.92, 710.632)" (in PDF)
** WARNING ** >> xxx "ps: 23.0 Resolution mul 72.27 div /CBarX1 exch def 
currentpo..."
---------------
None of the other drivers changebars knows about works with xdvipdfmx 
either, I guess for obvious reasons.

The minimal program to elicit those error msgs is attached below my 
signature.
-- 
	Mike Maxwell
	maxwell at umiacs.umd.edu
	"My definition of an interesting universe is
	one that has the capacity to study itself."
         --Stephen Eastmond

--------------minimal program follows----------------
\documentclass{report}
%\listfiles
\usepackage{ifxetex}
\usepackage{fontspec}
\usepackage{xltxtra}
\usepackage{changebar}

\begin{document}
foo
\cbstart{}baz\cbend{}
bar
\end{document}