linux: Update to 3.4.75

(cherry picked from commit c3db56527dccbf57c704351595c05e642dd0cf5b)
nss: Update to 3.15.3.1

http://www.mozilla.org/security/announce/2013/mfsa2013-117.html
(cherry picked from commit 72feb8e011a68524fa1c59e2a096fff122efa9f7)
linux: Update to 3.4.76

(cherry picked from commit 03ad7a081c6a8053f1ac891ce28c8a198a90dc4f)
nix: Backport bug fix to check NAR integrity

(cherry picked from commit b9dbfe7feba501dfe61ea1670bcdf274e9ca66f0)