Fixed compiler warnings to make code compile with gcc's -pedantic switch
Fixed compiler warnings to make code compile with gcc's -pedantic switch

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