@BeginExampleSession/@EndExampleSession do not respect plain_text_mode

[gwhitney]

If you save the attached .txt file as "tst/plaintextmode.tst" with respect to the current directory, and then execute the following GAP session:

gap> LoadPackage("AutoDoc");
─────────────────────────────────────────────────────────────────────────────
Loading  AutoDoc 2018.02.14 (Generate documentation from GAP source code)
by Sebastian Gutsche (http://wwwb.math.rwth-aachen.de/~gutsche/) and
   Max Horn (http://www.quendi.de/math).
Homepage: https://gap-packages.github.io/AutoDoc
─────────────────────────────────────────────────────────────────────────────
true
gap> SetInfoLevel(InfoGAPDoc, 0);
gap> AutoDocWorksheet( "tst/plaintextmode.tst", rec( dir := "tempdoc" ) );
Generating documentation in Directory("./tempdoc/")
gap> quit;

you indeed get a manual.pdf file (as also attached), and that manual does have an example block, but rather surprisingly, it is completely empty. On the other hand, if you prefix every line between the @BeginExampleSession and @EndExampleSession with #!, then you get the expected contents of the example block. This would appear to be a bug, that the state of plain_text_mode is not being respected in example sessions.

I will submit a pull request within a day with a proposed fix for this bug.
manual.pdf
plaintextmode.txt