#1218 Fixes to chapter 6 and 8

[Eugenio Di Lorenzo]

After generating the last PDF, I had to make some layout and truncation corrections.
I'm sorry to have to send back the same two files just updated, but trying to generate text and graphically structured pages with texinfo commands without being able to immediately see the result is truly exhausting for me.
Thanks as always for your patience and cooperation.

[Vincent (Bryan) Coen]

done