destructuring-bind doesn't handle &optional (arg 'default)

[Kalle Olavi Niemitalo]

In GNU Emacs 20.7.2 (i386-debian-linux-gnu, X toolkit)
 of Fri Apr 13 2001 on PC486
configured using `configure  i386-debian-linux-gnu --prefix=/usr 
--sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib 
--infodir=/usr/share/info --with-pop=yes --with-x=yes --with-x-toolkit=yes'

In defmacro*, optional arguments with default values work as expected:

ELISP> (require 'cl)
cl
ELISP> (defmacro* kon-test (&optional (arg 'default))
         `',arg)
kon-test
ELISP> (kon-test)
default
ELISP> (kon-test foo)
foo

However, the corresponding `destructuring-bind' form signals an error:

ELISP> (destructuring-bind (&optional (arg 'default))
           '()
         arg)
*** Eval error ***  Symbol's value as variable is void: bind-enquote
ELISP> (destructuring-bind (&optional (arg 'default))
           '(foo)
         arg)
*** Eval error ***  Symbol's value as variable is void: bind-enquote

I expected the first expression to return `default' and the
second to return `foo', like with the macro.  If I bind
`bind-enquote' around the form, it works (in interpreted code):

ELISP> (let ((bind-enquote nil))
         (destructuring-bind (&optional (arg 'default))
             '()
           arg))
default
ELISP> (let ((bind-enquote nil))
         (destructuring-bind (&optional (arg 'default))
             '(foo)
           arg))
foo

Thus I believe `bind-enquote' should be added in the list of
variables bound by the `destructuring-bind' macro.