Revert "; * lisp/subr.el (setq-local): Doc fix (bug#78644)."

This reverts commit cb9556d669.
Some of its parts were not supposed to be installed.

lisp/cus-edit.el

@@ -149,8 +149,7 @@
   (error nil))
 
 (condition-case nil
-    (unless (featurep 'cus-start)
-      (require 'cus-start))
+    (require 'cus-start)
   (error nil))
 
 (put 'custom-define-hook 'custom-type 'hook)

lisp/custom.el

@@ -699,8 +699,7 @@ The result is that the change is treated as having been made through Custom."
       (ignore-errors
         (require 'cus-load))
       (ignore-errors
-        (unless (featurep 'cus-start)
-          (require 'cus-start)))
+        (require 'cus-start))
       (dolist (load (get symbol 'custom-loads))
         (cond ((symbolp load) (ignore-errors (require load)))
 	      ;; This is subsumed by the test below, but it's much faster.

lisp/subr.el

@@ -161,12 +161,11 @@ of previous VARs.
     `(progn . ,(nreverse exps))))
 
 (defmacro setq-local (&rest pairs)
-  "Make each VARIABLE local to current buffer and set it to corresponding VALUE.
+  "Make each VARIABLE buffer-local and assign to it the corresponding VALUE.
 
 The arguments are variable/value pairs.  For each VARIABLE in a pair,
-make VARIABLE buffer-local in the current buffer and assign to it the
-corresponding VALUE of the pair.  The VARIABLEs are literal symbols
-and should not be quoted.
+make VARIABLE buffer-local and assign to it the corresponding VALUE
+of the pair.  The VARIABLEs are literal symbols and should not be quoted.
 
 The VALUE of the Nth pair is not computed until after the VARIABLE
 of the (N-1)th pair is set; thus, each VALUE can use the new VALUEs