Add macrocode as special case for syntax highlighting

[Skillmon]

Inside a DTX file the macrocode environment has a very special meaning as it starts and ends the portions of the file which will be added to the exported file.

For that reason this PR adds a highlighting group for % \begin{macrocode} (and \end) and links it to Special.

[lervag]

Thanks! Can you give an example .dtx file for this as well?

[Skillmon]

What do you exactly need the example .dtx file to contain?

[Skillmon]

Or rather: What do you need it for? Just as an example why the macrocode environment is special? Or for some tests? Should it be a minimal valid standalone .dtx file?

[lervag]

Ah, sorry, I need it for testing. I like to have a simple test file for more or less any feature. I can add the file myself, I just need to have some example of a relevant dtx file that uses the macrocode environment.

[Skillmon]

In that case, doesn't get more authoritative than the LaTeX kernel (though their .dtx files are big and probably more trouble than you'd need):

• from LaTeX3: https://github.com/latex3/latex3/blob/develop/l3kernel/l3tl.dtx#L1506
• from LaTeX2e: https://github.com/latex3/latex2e/blob/develop/base/classes.dtx#L78

As a simpler example, from one of my own smaller packages:

• https://github.com/Skillmon/ltx_clrstrip/blob/master/clrstrip.dtx#L271

[Rmano]

Identfirst? 😜 (The joke on Tex.sx chat is that it's the smallest package possible...)

https://mirrors.ctan.org/macros/latex/required/tools/indentfirst.dtx

[lervag]

Thanks! I added test files myself and merged this.