config: drop scripts that automake says are not independent

These three scripts are too closely tied to automake internals to
be independently useful.  In fact, automake would rather that
people did not mix the latest version of these scripts with older
versions of automake, as there is no effort being put into
maintaining backwards-compatibility when these scripts are updated.

The remaining scripts pulled from automake, such as mdate-sh or
depcomp, are independently useful, so a future patch may end up
reparenting those scripts to have gnulib instead of automake as
the master owner.

* config/srclist.txt: Drop elisp-comp, missing, and ylwrap.
* build-aux/elisp-comp: Delete.
* build-aux/missing: Likewise.
* build-aux/ylwrap: Likewise.
* modules/elisp-comp: Likewise.
* MODULES.html.sh: Drop mention of elisp-comp.
* NEWS: Mention this.

Signed-off-by: Eric Blake <eblake@redhat.com>