bug#31984: 26.1.50; IELM doesn't indent results printed with #

[Gemini Lasswell]

When the result of evaluation in IELM is something with a printed
representation beginning with #, such as a record or char-table,
it is pretty-printed without indentation.

To reproduce, M-x ielm RET and then evaluate this:

(require 'cl-lib)
(cl-defstruct (foo) a)
(make-foo :a (lambda (x) (- 1 x)))

Result:

#s(foo :a
(lambda
(x)
(- 1 x)))

If you do the same thing in Emacs 25, this is the result:

[cl-struct-foo
 (lambda
   (x)
   (- 1 x))]

Here are two other examples which when evaluated in IELM print
results without indentation in Emacs 26 and with indentation in Emacs 25:

char-acronym-table

(let ((ht (make-hash-table)))
  (puthash 1 '(a b c) ht)
  ht)

Oddly, Emacs 26's IELM does indent the result of this one:

(symbol-function 'ielm-process)