Fixes up Polonium to work with NO_DNA_RAD

Did a search through the codebase, thought it might be good to patch up
other things that touch the radiation variable.

code/modules/reagents/newchem/toxins.dm

@@ -15,7 +15,7 @@ datum/reagent/polonium
 
 datum/reagent/polonium/on_mob_life(var/mob/living/M as mob)
 	if(!M) M = holder.my_atom
-	M.radiation += 8
+	M.apply_effect(8, IRRADIATE)
 	..()
 	return
 
@@ -742,4 +742,4 @@ datum/reagent/ants/on_mob_life(var/mob/living/M as mob)
 	if(!M) M = holder.my_atom
 	M.adjustBruteLoss(2)
 	..()
-	return
+	return