xt_IDLETIMER: Add new netlink msg type for IDLETIMER.

Squashed commit of the following:

commit 3cfe1023c0999bd7bf5b991e82f5f14a39454969
Author: Ashish Sharma <ashishsharma@google.com>
Date:   Wed Feb 5 01:50:50 2014 +0000

    netfilter: xt_IDLETIMER: Revert to retain the kernel API format.

    Reverted Change-Id: Iaeca5dd2d7878c0733923ae03309a2a7b86979ca

    Change-Id: I0e0a4f60ec14330d8d8d1c5a508fa058d9919e07
    Signed-off-by: Ashish Sharma <ashishsharma@google.com>

commit bf204ad9814c621ef28686d736c79a3c6c5506d3
Author: Ashish Sharma <ashishsharma@google.com>
Date:   Mon Aug 13 11:38:49 2012 -0700

    netfilter: xt_IDLETIMER: Rename INTERFACE to LABEL in netlink notification.

    Signed-off-by: Ashish Sharma <ashishsharma@google.com>

commit 70fa6a5d5019638d46406b29789284923b4bf89f
Author: JP Abgrall <jpa@google.com>
Date:   Fri May 4 14:26:57 2012 -0700

    netfilter: xt_IDLETIMER: Use uevent instead of new netlink msg type

    Send netlink message notifications using a uevent with
      subsystem=xt_idletimer
      INTERFACE=...
      STATE={active,inactive}
    instead of needing a new netlink message type.
    Revert the netlink.h change added by commit
      beb914e987cbbd368988d2b94a6661cb907c4d5a

    Change-Id: I6881936bf754f3367ff3c8f6c1e9661cec0357d4
    Signed-off-by: JP Abgrall <jpa@google.com>

commit 43c75b7d23b947539508c8e9deb026333194d444
Author: Ashish Sharma <ashishsharma@google.com>
Date:   Thu Mar 29 13:02:27 2012 -0700

    xt_IDLETIMER: Add new netlink msg type for IDLETIMER.

    Send notifications when the label becomes active after an idle period.
    Send netlink message notifications in addition to sysfs notifications.

    Change-Id: I31677ef00c94b5f82c8457e5bf9e5e584c23c523
    Signed-off-by: Ashish Sharma <ashishsharma@google.com>

Change-Id: I04d0258bc52b284c8d8b40c53a65994c7464d443