#4684 lurkmathml does not typeset x_1 correctly

[Leo Butler]

The tex code does the following:

tex(x_1);

$$x_{1}$$

The mathml code slavishly follows the same pattern, which is wrong:

mathml(x_1);

<math xmlns="http://www.w3.org/1998/Math/MathML">  <msub><mi>x_</mi> <mn>1</mn></msub> </math>

If we follow the DWIM method that tex uses, then the underscore _ should be dropped from the mathml output.

[Leo Butler]

Fixed in commit 69981c5f6.