MathJax and MathML-in-SVG-in-MathML

MathJax failed to parse the 'inner'
MathML, which led to bad rendering.
This fixes the problem in Safari and
ameliorates it in Chrome. See
https://github.com/mathjax/MathJax/issues/896
for a discussion.
Merge branch 'bzr/golem' of /Users/distler/Sites/code/instiki