bug#8638: 24.0.50; Imenu should not include vacuous defvars

["Drew Adams" <drew.adams@oracle.com>]

> > OK, thanks.  But I wonder why you treated defvar differently from
> > defconst, defconstant, defcustom, defparameter, and
> > define-symbol-macro here.  Shouldn't the same thing apply to them?
> 
> There is no such thing as (defconst foo), or (defcustom foo); 
> the second argument is non-optional.

Yes, I know.

> So the reasoning which was used for defvar, i.e. that a defvar
> with an omitted second arg is commonly used just to silence the
> compiler, does not apply.

But the reasoning that such things, if they ever occurred, would not represent
proper definitions, so Imenu should not index them, holds.  They would represent
incorrect syntax (i.e., errors), and should not be indexed.

Anyway, I'm OK with them being falsely indexed, and I would agree if you made
the argument that we do not try to prevent indexing of incorrect syntax in
general.