Remove double `Generated from foo.m4sh' lines.

Remove double `Generated from foo.m4sh' lines.

We now require a modern Autoconf to bootstrap libtool, which
will add the `Generated by ...' boiler-plate automatically,
so we can remove the hand-rolled @configure_input@
substitutions we had been doing:
* clcommit.m4sh, libtoolize.m4sh, tests/defs.sh,
libltdl/config/announce-gen.m4sh, libltdl/config/ltmain.m4sh,
libltdl/config/mailnotify.m4sh: Remove @configure_input@.
* Makefile.am (edit): Remove configure_input substitution.
(libtoolize, libltdl/config/ltmain.sh, libltdl/m4/ltversion.m4)
(tests/defs): Don't set `$input' shell variable.
* Makefile.maint (announce_gen, libltdl/config/mailnotify)
(commit): Likewise.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>