ANDROID: netfilter: xt_IDLETIMER: Add new netlink msg type

Send notifications when the label becomes active after an idle period.
Send netlink message notifications in addition to sysfs notifications.
Using a uevent with
  subsystem=xt_idletimer
  INTERFACE=...
  STATE={active,inactive}

This is backport from common android-3.0
commit: beb914e9
with uevent support instead of a new netlink message type.

Bug: 120445672
Change-Id: I31677ef00c94b5f82c8457e5bf9e5e584c23c523
Signed-off-by: Ashish Sharma <ashishsharma@google.com>
Signed-off-by: JP Abgrall <jpa@google.com>
[astrachan: Folded the following changes into this patch:
            ee0b238fada5 ("netfilter: xt_IDLETIMER: time-stamp and suspend/resume handling.")
            728c058a495e ("netfilter: xt_IDLETIMER: Adds the uid field in the msg")
            5ebea489d44c ("netfilter: xt_IDLETIMER: Fix use after free condition during work")
            5ab69d7ba2c5 ("netfilter: xt_IDLETIMER: Use fullsock when querying uid")]
Signed-off-by: Alistair Strachan <astrachan@google.com>
[AmitP: get_monotonic_boottime() is dropped from mainline,
        use ktime_get_boottime() instead. Ref commit:
        97651640 ("y2038: remove unused time interfaces").

        timespec_add/timespec_del() are dropped from mainline too,
        437e78d3 "timekeeping: remove timespec_add/timespec_del"),
        which required minor refactoring using timespec64 APIs.]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>