* Makefile.in: Run autogen/copy_autogen if autogen.sh fails,

* Makefile.in: Run autogen/copy_autogen if autogen.sh fails,

to create 'configure'; problem reported by Andreas Schwab in
<http://lists.gnu.org/archive/html/emacs-devel/2012-09/msg00438.html>.
* autogen.sh: Exit with status 1 when failing due to missing tools,
reverting the 2012-09-10 change to this file.
* autogen/copy_autogen: Fail if one of the subsidiary actions fail.
Use 'cp -f' for the build-aux files, since the destinations are
typically read-only.