Introduced a new variable CONTIKI_OBJECTFILES in order to allow target-specific makesfile to add object files to the Contiki library which are not compiled from .c files but i.e. assembled from .S files.
Introduced a new variable CONTIKI_OBJECTFILES in order to allow target-specific makesfile to add object files to the Contiki library which are not compiled from .c files but i.e. assembled from .S files.

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