kernel: stable updates

 - (3.13 branch omitted, not in release-13.10)
 - 3.12 stable:   3.12.11 -> 3.12.12
 - 3.10 longterm: 3.10.29 -> 3.10.31
 - 3.4  longterm: 3.4.79  -> 3.4.81

Signed-off-by: Austin Seipp <aseipp@pobox.com>
(cherry picked from commit a1dc5ea7072158fb2371108210ccad5eda5c8f41)

Conflicts:
	pkgs/os-specific/linux/kernel/linux-3.10.nix
	pkgs/os-specific/linux/kernel/linux-3.12.nix
	pkgs/os-specific/linux/kernel/linux-3.4.nix
	pkgs/os-specific/linux/kernel/linux-3.9.nix