In addition, keep gum handy. Offer him a piece every time he approaches you. I take gum/mints whenever they are offered out of sheer paranoia.
I'm not sure this boar will take the hint, but it can't hurt. I'd be willing to bet that when you do go to HR, they will not be surprised.
Also, spitting food on you? Cringe! I'd step quickly away and say, "Pardon me, there's some rice/noodles/whatever on my shirt." Gross.