bug#4755: 23.1; case where `C-M-x' on defcustom doesn't seem to work

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

> tags 4755 unreproducible
> quit

> Can't reproduce on Emacs 23.4, perhaps it was fixed?

I just reproduced it using Emacs 25, from emacs -Q. Here's
some of the proof of a problem:

toto's value is shown below.

Documentation:
...

You can customize this variable.

Value: (("foo" (f1 f2) f3) ("bar" (b1 b2) b3))
Original value was 
(("foo"
  (f1 f2)
  f3)
 ("bar"
  (b1 b2)
  b3)
 ("toto"
  (f1 f2 f3)
  nil))

`foo', not `toto' was customized, and the Value shown
here is correct. But the "Original value" is incorrect.
The "Original value" shown is the new, current value
of `foo'.  `toto' never had, as still does not have,
that "Original value".

For the above, I did not even get to the part of the
recipe that calls for using `C-M-x' on the `toto'
defcustom.  All I did was customize `foo' and set it
for the session.

Then, doing `C-M-x' does correctly show `toto' as
having the same value as `foo'.

So if you prefer, yes, the bug as reported seems to be
fixed.  But there is another bug, shown above:
customizing `foo' changes the "Original value" part
of the output of `C-h v' for `toto'.

Something is still amiss in the state of Denmark...