Copy empty Presentation MathML elements verbatim rather than inserting <mi> with the name of the element, as neede for Content MathML.  Resolves issue #1323.
Copy empty Presentation MathML elements verbatim rather than inserting <mi> with the name of the element, as neede for Content MathML.  Resolves issue #1323.

thomasjm/MathJax,dpvc/MathJax,jinntrance/mathjax,thomasjm/MathJax,jinntrance/mathjax,GerHobbelt/MathJax,thomasjm/MathJax,GerHobbelt/MathJax,thomasjm/MathJax,thomasjm/MathJax,wikimedia/MathJax