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.)
1 job for master in 3 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #2057
test-all

00:00:03

 
Name Stage Failure
failed
test-all Test There has been a runner system failure, please try again
Running with gitlab-runner 11.6.0 (f100a208)
on gitlab-runner-docker cff9d373
Using Docker executor with image debian:stretch ...
Pulling docker image debian:stretch ...
Using docker image sha256:8d31923452f8b79ae91b01568d28c90e7d667a9eaff9734c6faeb017b0efa8d0 for debian:stretch ...
ERROR: Job failed (system failure): Error response from daemon: failed to start shim: exec: "docker-containerd-shim": executable file not found in $PATH: unknown (executor_docker.go:1018:0s)