TeXmacs fixes

[d-torrance]

This includes @mgubi's proposed fix for #2534 and also fixes the reported matrix display issue. This was a small bug in mathML(MatrixExpression) where we were trying to just display the first row.

Before

After

@mgubi, @bztd: Thoughts?

[bztd]

I will apply the changes to the stable version and do testing.

[d-torrance]

I added a couple more commits adding AfterPrint support for TeXmacs mode. So for example, we get the source/target info for matrices like we do with the standard and webapp modes:

[mgubi]

I do not know Macauly2, so I trust you :) the output seems correct. What about the matrix which includes symbolic entries and is in the TeXmacs' help for the M2 Plugin? (Help->Plugin->Macauly2).

[d-torrance]

Yes, that works!

[mgubi]

I gave a look at the web app. Since TeXmacs can read plugin output in HTML format, one could reuse the code written for the web app to produce HTML output to send to texmacs. Most of the features of the web app could be emulated in TeXmacs.

[d-torrance]

The webapp mode outputs html, but the math is mostly $-delimited LaTeX that is rendered using Javascript (KaTeX). For example:

i2 : 2:0matrix {{1, 2}, {3, 4}}

o2 = $\left(\!\begin{array}{cc}
1&2\\
3&4
\end{array}\!\right)$

o2 : <span><samp class="token class-name">Matrix</samp> ${\mathbb Z}^{2}\,\longleftarrow \,{\mathbb Z}^{2}$</span>

Is that something that TeXmacs would support? Otherwise, I think the current MathML-based implementation mostly works.

[mgubi]

IIRC TeXmacs imports correctly Wikipedia pages with math (which should be MathJax). Alternatively one needs to switch to "latex" input in those pieces. TeXmacs supports "html", "latex" and some others.

[bztd]

In my local tests M2 already works in TeXmacs.

[d-torrance]

Great! I'll go ahead and merge this