support/gnuconfig: update config.{guess, sub} to a newer version

We need more recent versions of config.guess and config.sub in order
to support the aarch64 architecture. Otherwise, all autoconf packages
fail to build with failures like:

  http://autobuild.buildroot.org/results/abcdbe1aaf1c203c82dc3e4ec8c002b9b9e550e0/build-end.log



We take this opportunity to turn the config.* patches into proper Git
patches, and note which Git commit of the config.git repository we
used as the original source.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>