backports: backport ieee802154 6lowpan support down to 3.5

backports: backport ieee802154 6lowpan support down to 3.5

Commit 633fc86ff62 added the ieee802154_6lowpan namespace
and 7240cdec60b extended it (as on linux-next next-20140311).
Its important to note though that 633fc86ff62 also extends the
global net namespace. Since we cannot extend the global net
namespace we define our own backport namespace for 6lowpan
that can be used only be used by our backported subsystems,
nothing more. Since ieee802154_6lowpan requires support for
net_get_random_once() which uses static keys and a slew of
new skb fragment support we simply require at least 3.5 to
use 6lowpan. I did my best effort to backport this to kernels
older than 3.5 but quickly ran into a slew of hairy issues.

The last thing we needed to address was usage of the helper
inet_frag_evictor() added by Alexander via commit 6b102865e7
through v3.7. Since we can't backport that with macros or
inline helpers we add a patch to carry the changes there. If
that grows we can consider using Coccinelle.

If you are going to try to backport 6lowpan to kernels older
than 3.5 be warned that the litmus test for patches will be
to pass ckmake --allyesconfig for all supported kernels for
every patch you provide.

Cc: Alexander Aring <alex.aring@gmail.com>
Cc: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: linux-zigbee-devel@lists.sourceforge.net
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>