netsniff-ng: Fix build against glibc 2.26

The build fails first of all because it cannot find the function body
for __builtin_memset. In glibc 2.26 this is available via inclusion of
string.h.

Another failure was that UINT64_MAX wasn't available in staging/tools.c,
which is fixed again by inclusion of stdint.h.

Signed-off-by: aszlig <aszlig@nix.build>
Cc: @nckx

pkgs/tools/networking/netsniff-ng/default.nix

@@ -14,6 +14,8 @@ stdenv.mkDerivation rec {
     sha256 = "1lz4hwgwdq3znlqjmvl7cw3g3ilbayn608h0hwqdf7v2jq6n67kg";
   };
 
+  patches = [ ./glibc-2.26.patch ];
+
   buildInputs = [ bison flex geoip geolite-legacy libcli libnet libnl
     libnetfilter_conntrack libpcap libsodium liburcu ncurses perl
     pkgconfig zlib ];