[Therion] therion book revision marking

[Martin Budaj]

> Is it easy to highlight latest revisions to the Therion Book each time it is
> released?
>
> Perhaps a line in the margin or something?

We have discussed it already, but it seemed to be equivalently
sufficient to start with reading CHANGES file when new version is
released to be informed about the changes and then find the
corresponding passages in the therion book (e.g. by searching for a
new keyword).

Alternatively you could automatically compare old and new versions of
thbook. For source code (*.tex files) or PDF-to-text export it is easy
using diff on the command lines or some advanced text editor. There
are also tools for comparing PDF files, but I am not sure if any of
them is free.

Martin