Fix out-of-source make-dist problems

Problem with jisx2131-filter reported by Phillip Lord in:
* admin/charsets/ (SED_SCRIPT):
Put it in $(srcdir), which is not necessarily the working directory.
($(SED_SCRIPT)): Rename from jisx2131-filter.  All uses changed.
(clean): Do not remove SED_SCRIPT.
(extraclean): Remove it here instead.
* make-dist (possibly_non_vc_files): Remove src/emacs-module.h.
Although it is portable and could be distributed in the tarball,
it's too much hassle to do that, so let each builder make it.
1 job for master in 3 seconds (queued for 2 seconds)
Status Job ID Name Coverage
failed #2050


Name Stage Failure
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)