6lowpan: introduce new net/6lowpan directory

6lowpan: introduce new net/6lowpan directory

This patch moves generic code which is used by bluetooth and ieee802154
6lowpan to a new net/6lowpan directory. This directory contains generic
6LoWPAN code which is shared between bluetooth and ieee802154 MAC-Layer.

This is the IPHC - "IPv6 Header Compression" format at the moment. Which
is described by RFC 6282 [0]. The BLTE 6LoWPAN draft describes that the
IPHC is the same format like IEEE 802.15.4, see [1].

Futuremore we can put more code into this directory which is shared
between BLTE and IEEE 802.15.4 6LoWPAN like RFC 6775 or the routing
protocol RPL RFC 6550.

To avoid naming conflicts I renamed 6lowpan-y to ieee802154_6lowpan-y
in net/ieee802154/Makefile.

[0] http://tools.ietf.org/html/rfc6282
[1] http://tools.ietf.org/html/draft-ietf-6lowpan-btle-12#section-3.2
[2] http://tools.ietf.org/html/rfc6775
[3] http://tools.ietf.org/html/rfc6550

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>