[XeTeX] Bug with Quotes at Sentence End

[Joel C. Salomon]

Minimal example:

% !TEX TS-program = xelatex
% !TEX encoding = UTF-8

\documentclass[12pt]{minimal}
\usepackage{fontspec,xunicode,xltxtra}

\begin{document}
Here are a few sentences ending in full-stops.
Notice the extra space at the end of each sentence,
due to not using \textsf{\textbackslash frenchspacing}.
“But this does not carry over if the sentence end
is within quotation marks.”
But it should.

Here are a few sentences ending in full-stops.
Notice the extra space at the end of each sentence,
due to not using \textsf{\textbackslash frenchspacing}.
``But this does not carry over if the sentence end
is within quotation marks.''
But it should.
\end{document}

I’d guess some of the Unicode quote characters need to have the correct
\spacefactor associated with them.

—Joel Salomon