TradeSkill recipes now can have optional ingredients

[bsmorgan]

Has anyone deciphered how to get information about these optional ingredients? In Blizzard_TradeSkillDetails.lua (around line 541) I found:

		local optionalReagentSlots = C_TradeSkillUI.GetOptionalReagentInfo(self.selectedRecipeID);
		local numOptionalReagentSlots = #optionalReagentSlots;
		local hasOptionalReagentSlots = numOptionalReagentSlots > 0;

After that, my head starts to hurt trying to decipher anymore.