Update GCC to autoconf 2.69, automake 1.15.1

[Thomas Koenig]

Am 31.10.18 um 04:26 schrieb Joseph Myers:
> This patch (diffs to generated files omitted below) updates GCC to use
> autoconf 2.69 and automake 1.15.1.

I think this should fix PR 82856.  Maybe you could confirm that this
restores automake functionality with perl 5.6.26, and mention the PR
in the ChangeLog.

> 
> Makefile.am:48: warning: source file 'caf/single.c' is in a subdirectory,
> Makefile.am:48: but option 'subdir-objects' is disabled
> automake: warning: possible forward-incompatibility.
> automake: At least a source file is in a subdirectory, but the 'subdir-objects'
> automake: automake option hasn't been enabled.  For now, the corresponding output
> automake: object file(s) will be placed in the top-level directory.  However,
> automake: this behaviour will change in future Automake versions: they
> will
> automake: unconditionally cause object files to be placed in the same subdirectory
> automake: of the corresponding sources.
> automake: You are advised to start using 'subdir-objects' option throughout your
> automake: project, to avoid future incompatibilities.
> 
> I think it's best for the relevant maintainers to add subdir-objects
> and do any other associated Makefile.am changes needed.  In some cases
> the paths in the warnings involved ../; I don't know if that adds any
> extra complications to the use of subdir-objects.

I'm not an automake expert, but I hope to be able to figure out
what is needed.  If not, I guess I'll just ask :-)

What is the plan for the previous branches?  Currently, it is necessary
to keep around a special version of automake etc for
--enable-maintainer-mode to work.  Backporting a patch which
involves regeneration of files in libgfortran/generated from
the files in libgfortan/m4 would then require keeping two versions
of the relevant tools around, and switching between them.

Would it make sense to backport because of this?

Thanks for your efforts!

Regards

	Thomas