buildroot

libmemcached: fix build with gcc 7.x

This commit adds a patch to the libmemcached package that fixes the
build with gcc 7.x. Since libmemcached is barely maintained upstream,
the patch comes from the Fedora packages.

Fixes:

  http://autobuild.buildroot.net/results/872b8e0e6a24cbc96e3ad9e0b8b47acdf6160ce0/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
(cherry picked from commit 8786ac28058aa553cfa8adc176952143af630af6)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>