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>

package/libmemcached/0005-fix-pointer-comparaison.patch

@@ -0,0 +1,30 @@
+Fix pointer comparaison
+
+opt_servers is a pointer, not a boolean, so testing against false to
+know if the pointer is NULL no longer works with the more strict gcc
+7.x checks.
+
+[Taken from http://pkgs.fedoraproject.org/cgit/rpms/libmemcached.git/plain/libmemcached-build.patch.]
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+
+diff -up ./clients/memflush.cc.old ./clients/memflush.cc
+--- ./clients/memflush.cc.old	2017-02-12 10:12:59.615209225 +0100
++++ ./clients/memflush.cc	2017-02-12 10:13:39.998382783 +0100
+@@ -39,7 +39,7 @@ int main(int argc, char *argv[])
+ {
+   options_parse(argc, argv);
+ 
+-  if (opt_servers == false)
++  if (!opt_servers)
+   {
+     char *temp;
+ 
+@@ -48,7 +48,7 @@ int main(int argc, char *argv[])
+       opt_servers= strdup(temp);
+     }
+ 
+-    if (opt_servers == false)
++    if (!opt_servers)
+     {
+       std::cerr << "No Servers provided" << std::endl;
+       exit(EXIT_FAILURE);