Manually mirroring WriteBarrier.S from github
Manually mirroring WriteBarrier.S from github

[tfs-changeset: 1547563]

sandreenko/corert,sandreenko/corert,kyulee1/corert,schellap/corert,kyulee1/corert,gregkalapos/corert,schellap/corert,botaberg/corert,manu-silicon/corert,botaberg/corert,mjp41/corert,manu-silicon/corert,yizhang82/corert,sandreenko/corert,gregkalapos/corert,yizhang82/corert,kyulee1/corert,yizhang82/corert,gregkalapos/corert,mjp41/corert,schellap/corert,kyulee1/corert,tijoytom/corert,yizhang82/corert,krytarowski/corert,manu-silicon/corert,shrah/corert,tijoytom/corert,krytarowski/corert,manu-silicon/corert,tijoytom/corert,mjp41/corert,botaberg/corert,sandreenko/corert,krytarowski/corert,shrah/corert,schellap/corert,mjp41/corert,manu-silicon/corert,tijoytom/corert,krytarowski/corert,shrah/corert,schellap/corert,mjp41/corert,botaberg/corert,gregkalapos/corert,shrah/corert