Upgrading autoconf and automake

[Pietro Monteiro via Gdb <gdb@sourceware.org>]

I decided to try upgrading autoconf and automake to the latest
available versions, respectively 2.73 and 1.19*. I did the upgrade for
GCC put the result in a branch on the forge
(https://forge.sourceware.org/pietro/gcc.git branch upgrade-autotools).

I also did the the upgrade for binutils-gdb tree and put it in a
branch on the forge too
(https://forge.sourceware.org/pietro/binutils-gdb.git branch
upgrade-autotools).

So far I did only some basic testing. The patch at the tip of that
branch has a changes to libiberty configure.ac that I still need to
sent for review.

One point that came up in the discussion about this upgrade in the GCC
mailinglist[1] is that binutils requires C99. So I want to make sure
we aren't regressing there.

What kind of testing should be done? Are other people able to help
here, specially for targets that don't use the GNU toolchain?

Thanks,
Pietro

* Automake 1.20 was just released. But I haven't looked into the
  release notes and I won't try to upgrade to it unless someone knows
  of good reason for it.

[1] https://inbox.sourceware.org/gcc/18b284b3-1b50-481a-a7ee-6e3e12073df0@app.fastmail.com/t/#u