Brought back mt.c which I had removed with revision 1.12 now that we have a cpu/native implementation of mtarch.c.
Brought back mt.c which I had removed with revision 1.12 now that we have a cpu/native implementation of mtarch.c.

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