There is no new autoconf release, and it seems like there will unlikely be one
<http://lists.gnu.org/archive/html/autoconf/2016-07/msg00017.html>.

This will allow us to support <arch>-apple-ios properly.

These have been taken from
- http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess
- http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub

Reviewers: austin, hvr, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3558