Update GCC to autoconf 2.69, automake 1.15.1

[Joseph Myers]

On Wed, 31 Oct 2018, Eric Gallager wrote:

> > Index: zlib/Makefile.am
> > ===================================================================
> > --- zlib/Makefile.am	(revision 265631)
> > +++ zlib/Makefile.am	(working copy)
> > @@ -1,6 +1,6 @@
> >  ## Process this file with automake to create Makefile.in.
> >
> > -AUTOMAKE_OPTIONS = 1.8 cygnus
> > +AUTOMAKE_OPTIONS = foreign
> 
> To get the modern equivalent of "cygnus" you need not just the
> "foreign" option (which you already have), but also the "no-dist"
> option in AUTOMAKE_OPTIONS.

As this is code shared with binutils-gdb, I was copying the change made 
there.  (Plus the include of $(top_srcdir)/../multilib.am because zlib can 
be built as a target module in GCC.)

-- 
Joseph S. Myers
joseph@codesourcery.com