bug#33566: 26; `group' :type for defcustom

[Drew Adams]

It seems like defcustom composite :type `group' does not work.

See https://emacs.stackexchange.com/q/46357/105.

emacs -Q

(defcustom foo '(1 2 3)
  "..."
  :type '(group integer integer integer)
  :group 'emacs)

M-x customize-option foo

Shows this message in *Messages*:

custom-variable-value-create: Bad format

And buffer *Customize Option: Foo* is not complete.  I see only this:

------------8<----------------

Custom settings cannot be saved; maybe you started Emacs with '-q'.
For help using this buffer, see Easy Customization in the Emacs manual.

                                          Search 

Operate on all settings in this buffer:
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------------8<----------------

The doc says that :type `group' should be very similar to :type `list',
but without tags.

See also this bug:
https://lists.gnu.org/archive/html/emacs-pretest-bug/2007-06/msg00067.html

In GNU Emacs 26.1 (build 1, x86_64-w64-mingw32)
 of 2018-05-30
Repository revision: 07f8f9bc5a51f5aa94eb099f3e15fbe0c20ea1ea
Windowing system distributor `Microsoft Corp.', version 10.0.16299
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''