bug#35372: Describe all types of safe-local-variable-values

[積丹尼 Dan Jacobson]

"safe-local-variable-values is a variable defined in ‘files.el’.

List variable-value pairs that are considered safe.
Each element is a cons cell (VAR . VAL)..."

No,only a few are like that

x((eval picture-movement-down)
x (eval register-file-header-action "// @version[       ]* " 
'update-write-count)
  (dired-omit-mode . t)
  (picture-vertical-step . 1)
  (picture-horizontal-step . 0)
  (sh-indentation . 2)
  (dired-actual-switches . "-ogta")
  (dired-actual-switches . "-ogt")
  (dired-actual-switches . "-og")
  (truncate-lines . 1)
y (make-backup-files))

Others either don't have a "." (x), or don't have a ". VAL" (y).

So the docstring should explain them too.