Added a macro for checking if an address is link local.
Added a macro for checking if an address is link local.

arurke/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,bluerover/6lbr,bluerover/6lbr,arurke/contiki,bluerover/6lbr,bluerover/6lbr,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr