Fix TODO to convert defvar with leading '*' to defcustom

Fix TODO to convert defvar with leading '*' to defcustom

* etc/TODO: Remove done TODO to remove '*' from defvar.
* doc/misc/gnus.texi: Remove leading '*' from defvar example.
* lisp/kermit.el (kermit-esc-char): Convert to defcustom.
* lisp/desktop.el (desktop-header):
* lisp/obsolete/cc-compat.el (c-indent-level)
(c-brace-imaginary-offset, c-brace-offset, c-argdecl-indent)
(c-label-offset, c-continued-statement-offset)
(c-continued-brace-offset): Remove leading '*' from docstring.
* lisp/progmodes/dcl-mode.el: Remove leading '*' from docstring in
comment.
* test/manual/cedet/tests/test.el: Add comment asking if example of
defvar with leading '*' should be removed.
(Bug#35994)  (The previous commit is also for the same bug.)