libmemcached: fix build failure with automake 1.15+

libmemcached: fix build failure with automake 1.15+

Adding a patch to move AC_CONFIG_AUX_DIR up a few lines so the autotools
can find it.

This patch is based on the same solution adopted by Debian:

  https://lists.debian.org/debian-release/2014/11/msg01231.html

This will prevent a build failure like this one caused by a version bump
of the automake package:

configure: error: cannot find install-sh, install.sh, or shtool in "."
"./.." "./../.."

Related:
  http://lists.busybox.net/pipermail/buildroot/2015-January/116604.html

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>