bug#28729: 26.0.60; Incorrect Edebug spec for gv-define-setter

[Gemini Lasswell]

The Edebug spec for gv-define-setter is incorrect. It should use
:name, so Edebug doesn't confuse it with the getter, and it should use
def-body instead of body. To reproduce the problem, put this bit of
code into *scratch*:

(defun obo-ref (a idx)
  (aref a (1- idx)))

(gv-define-setter obo-ref (val a idx)
  `(aset ,a (1- ,idx) ,val))

(defvar my-array [ 10 20 30 40 ])

(defun set-first-elem (n)
  (setf (obo-ref my-array 1) n))

Then:

M-x edebug-all-defs RET
M-x eval-buffer RET

Result: Eager macro-expansion failure: (wrong-type-argument consp nil)

M-: (obo-ref my-array 3) RET
SPC SPC

Result: Edebug starts stepping through the setter, then quits with
"Source has changed - reevaluate definition of obo-ref".