Improve and make use of 'definition' environment

[henrikt-ma]

Fixes #2570.

[HansOlsson]

Looks good to me. I have two minor concerns in the synchronous chapter (which had severe problems before as well):

• The figures for piecewise-constant (etc) look a bit odd with the new format. And 16.3 seems redundant with 16.4. One possibility would be to replace those three figures by one larger figure containing everything; and "hold(r)" for the green dotted line.
• The style of "[The input argument is a] component expression" looks a bit odd, but I don't know how to best format that - maybe it was better without []?. Clearly "component expression" is the main part, but the definition above already defined "component expression".

[henrikt-ma]

• The style of "[The input argument is a] component expression" looks a bit odd, but I don't know how to best format that - maybe it was better without []?. Clearly "component expression" is the main part, but the definition above already defined "component expression".

Yes, it is really hard to make this nice. I think the real problem here is that the the terms being defined are just too long because of the need to also give that context (the input argument is a) as part of the definition. I think one can take a step back here, and see that we aren't actually defining three new concepts here, just putting already defined concepts in a particular context. Let's see what that would look like…

[henrikt-ma]

• The figures for piecewise-constant (etc) look a bit odd with the new format. And 16.3 seems redundant with 16.4. One possibility would be to replace those three figures by one larger figure containing everything; and "hold(r)" for the green dotted line.

I'm working on it, but it takes time to find a solution that works with both \autoref and LaTeXML… I'd say it's better to merge now without waiting for the solution.