Bug: LaTeX fragments export to invalid XHTML

Bug: LaTeX fragments export to invalid XHTML

[Uriel Avalos]

This is the sample file:

  * Hello world
  \begin{align*}
  x&=\frac{-b^2\pm\sqrt{b^2-4ac}}{2a}
  \end{align*}

When you validate the resulting HTML file at the w3c site
(http://validator.w3.org/check), it fails the check.

If you recall, when org-export-with-latex-fragments is set to dvipng,
it produces PNG images with the ALT attribute equal to the
corresponding LaTeX equation. In this case, the resulting IMG tag
is:

<img src="<filenameofPNG>"
alt="\begin{align*}x&=\frac{-b^2\pm\sqrt{b^2-4ac}}{2a}\end{align*}"/>

Apparently, you can't have unescaped & (ampersands) in an ALT tag.
Thus, the resulting HTML file fails to validate.