Assign the fixed user id 1 to the user created by initdb.
A stand-alone backend will always set the user id to 1.
(Consequently, the name of that user is no longer important.)

In stand-alone mode, the user id 1 will have implicit superuser
status, to allow repairs even if there are no users defined.

Print a warning message when starting in stand-alone mode when no
users are defined.

Disallow dropping the current user and session user.

Granting/revoking superuser status also grants/revokes usecatupd.
(Previously, it would never grant it back.  This could lead to "deadlocks".)

CREATE USER and CREATE GROUP will start allocating user ids at 100
(unless explicitly specified), to prevent accidental creation of a
superuser (plus some room for future extensions).

 adjustments. Note that many tables are being abused with *really* long
 description columns. Should probably shrink those columns to be more
 concise, and move some of the info to follow-on reference notes.

names for the HTML files (e.g., not x4856.htm).

management

reference page to new configuration system. Big update to administrator's
guide, chapters Runtime environment, Client authentication, and User
management, the latter two were part of the old Security chapter.