autodist: remove obscure, very seldom used, or obsolescent files

autodist: remove obscure, very seldom used, or obsolescent files

This removes obscure and undocumented crufty behaviour.

* NG-NEWS: Update.
* automake.in (@common_file): Don't automatically distribute the
'BACKLOG' nor 'libversion.in' files anymore.  Also, don't list the
contents of @libtool_sometimes; in fact ...
(@libtool_sometimes): ... remove this altogether: the 'ltconfig.in'
file has been gone since at least version 1.3d (2001-04-02), according
to Libtool's NEWS file (more precisely, it has been removed in commit
e927e431 of 2000-09-06, "libtool.m4 now contains a version of the code
that used to run from ltconfig, so that ltmain.sh and then libtool are
generated at configure time"); and the files ltcf-c.sh, ltcf-cxx.sh and
ltcf-gcj.sh has only been present in the 'multi-language-branch' branch
of the libtool repository (abandoned since 2001, see commit d7f080d6),
and they have never been truly merged into master nor any supported
libtool release.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>