Install iucode-tool from wheezy-backports.

Now that we have the appropriate configuration to make good use of it,
here we go.

Besides, it's now required by intel-microcode, so we cannot skip it anymore.

config/chroot_apt/preferences

-Explanation: We want firmware for all CPUs, not only the one we build on.
-Package: iucode-tool
-Pin: release o=Debian
-Pin-Priority: -1
-
 Explanation: override deb.tails.boum.org's Squeeze -specific package.
 Package: aircrack-ng
 Pin: release o=Debian Backports,n=wheezy-backports
@@ -89,6 +84,10 @@ Package: intel-microcode
 Pin: release o=Debian Backports,n=wheezy-backports
 Pin-Priority: 999
 
+Package: iucode-tool
+Pin: release o=Debian Backports,n=wheezy-backports
+Pin-Priority: 999
+
 Package: klibc-utils
 Pin: release o=Debian,n=wheezy
 Pin-Priority: 999