• Change the title of the /etc/group section. This talks about more than just /etc/group.
• Update the example of a missing user/group that caused breakage during builds, to mention the recent smmsp troubles.
• Add a note (by Martin Heinen) that mentions mergemaster's -p option for prebuildworld merges of files in /etc.

PR: docs/36773
Submitted by: gshapiro, Martin Heinen <martin@sumuk.de>