Update packaging to standards version 3.9.5

Resolve this lintian warning:

	W: spl-linux source: ancient-standards-version 3.9.3 (current is 3.9.5)
Backport: mutex-force-serialization-on-mutex_exit-to-fix-races.patch

Commit: zfsonlinux/zfs@a3c1eb77721a0d511b4fe7111bb2314686570c4b
From: Chunwei Chen <tuxoko@gmail.com>
Date: Fri, 19 Dec 2014 11:31:59 +0800
Subject: mutex: force serialization on mutex_exit() to fix races

It is known that mutexes in Linux are not safe when using them to
synchronize the freeing of object in which the mutex is embedded:

http://lwn.net/Articles/575477/

The known places in ZFS which are suspected to suffer from the race
condition are zio->io_lock and dbuf->db_mtx.

* zio uses zio->io_lock and zio->io_cv to synchronize freeing
  between zio_wait() and zio_done().
* dbuf uses dbuf->db_mtx to protect reference counting.

This patch fixes this kind of race by forcing serialization on
mutex_exit() with a spin lock, making the mutex safe by sacrificing
a bit of performance and memory overhead.

This issue most commonly manifests itself as a deadlock in the zio
pipeline caused by a process spinning on the damaged mutex.  Similar
deadlocks have been reported for the dbuf->db_mtx mutex.  And it can
also cause a NULL dereference or bad paging request under the right
circumstances.

This issue any many like it are linked off the zfsonlinux/zfs#2523
issue.  Specifically this fix resolves at least the following
outstanding issues:

zfsonlinux/zfs#401
zfsonlinux/zfs#2523
zfsonlinux/zfs#2679
zfsonlinux/zfs#2684
zfsonlinux/zfs#2704
zfsonlinux/zfs#2708
zfsonlinux/zfs#2517
zfsonlinux/zfs#2827
zfsonlinux/zfs#2850
zfsonlinux/zfs#2891
zfsonlinux/zfs#2897
zfsonlinux/zfs#2247
zfsonlinux/zfs#2939

Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Backported-by: Darik Horn <dajhorn@vanadac.com>
Closes #421

Conflicts:
        include/sys/mutex.h