Fix customization of text-quoting-style

* lisp/cus-edit.el (custom-guess-type, custom-variable-documentation):
* lisp/wid-edit.el (widget-docstring):
Get raw docstring here since it’s cooked later and should not be
cooked twice.
* lisp/cus-edit.el (custom-group-value-create):
Cook the docstring before inserting it.
* lisp/cus-start.el (text-quoting-style): Quote the customization
docstrings according to the new rules.  Give curved examples.

lisp/cus-edit.el

@@ -633,7 +633,7 @@ if that fails, the doc string with `custom-guess-doc-alist'."
 	(setq found (nth 1 current)
 	      names nil)))
     (unless found
-      (let ((doc (documentation-property symbol 'variable-documentation))
+      (let ((doc (documentation-property symbol 'variable-documentation t))
 	    (docs custom-guess-doc-alist))
 	(when doc
 	  (while docs
@@ -2457,7 +2457,7 @@ If INITIAL-STRING is non-nil, use that rather than \"Parent groups:\"."
   "Return documentation of VARIABLE for use in Custom buffer.
 Normally just return the docstring.  But if VARIABLE automatically
 becomes buffer local when set, append a message to that effect."
-  (format "%s%s" (documentation-property variable 'variable-documentation)
+  (format "%s%s" (documentation-property variable 'variable-documentation t)
 	  (if (and (local-variable-if-set-p variable)
 		   (or (not (local-variable-p variable))
 		       (with-temp-buffer
@@ -3995,7 +3995,7 @@ If GROUPS-ONLY is non-nil, return only those members that are groups."
 	 (members (custom-group-members symbol
 					(and (eq custom-buffer-style 'tree)
 					     custom-browse-only-groups)))
-	 (doc (widget-docstring widget)))
+	 (doc (substitute-command-keys (widget-docstring widget))))
     (cond ((and (eq custom-buffer-style 'tree)
 		(eq state 'hidden)
 		(or members (custom-unloaded-widget-p widget)))

lisp/cus-start.el

@@ -224,11 +224,9 @@ Leaving \"Default\" unchecked is equivalent with specifying a default of
 	     (text-quoting-style
               help
               (choice
-               (const :tag "Quote with curved single quotes" curve)
-               (const :tag "Quote with straight apostrophes 'like this'"
-                      straight)
-               (const :tag "Quote with grave accent and apostrophe `like this'"
-                      grave)
+               (const :tag "Quote with curved single quotes \\=‘like this\\=’" curve)
+               (const :tag "Quote with straight apostrophes \\='like this\\='" straight)
+               (const :tag "Quote with grave accent and apostrophe \\=`like this\\='" grave)
                (const :tag "Use curved quotes if displayable, grave accent and apostrophe otherwise" nil))
               "25.1")
              ;; dosfns.c

lisp/wid-edit.el

@@ -1676,7 +1676,7 @@ as the argument to `documentation-property'."
 		   (cond ((functionp doc-prop)
 			  (funcall doc-prop value))
 			 ((symbolp doc-prop)
-			  (documentation-property value doc-prop)))))))
+			  (documentation-property value doc-prop t)))))))
     (when (and (stringp doc) (> (length doc) 0))
       ;; Remove any redundant `*' in the beginning.
       (when (eq (aref doc 0) ?*)