libiscsi: add patch to fix largefile related issues

This commit adds a patch to libiscsi, to fix largefile related issues
occuring in two situations:

 * glibc toolchains, due to the way _FILE_OFFSET_BITS=64 is handled,
   by declaring the *64() functions as aliases to the non-64*() ones.

 * uClibc toolchains without largefile support.

First problem was visible in:

  http://autobuild.buildroot.org/results/b52/b52782c7ada0db098620bd8eceedd7b84515446b/

Second problem was visible in:

  http://autobuild.buildroot.org/results/23c/23c27fc7c4836dfd2527e52d95d5e72905ece7be/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>