libiscsi: bump version to 1.12.0

This commit bumps libiscsi to version 1.12.0, which requires a few
changes:

 - A number of patches to get libiscsi to build properly.
 - The removal of the popt dependency, which is no longer needed.
 - The removal of unnecessary spaces for alignment of variable
   definitions in libiscsi.mk.

Fixes:

  http://autobuild.buildroot.org/results/72f/72f389edf9c5a7e35d01dc4f76fd6dd0d8110f20/



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