AGOS: Add setLoyaltyRating() function
AGOS: Move most off the loyalty rating workaround to off_b2Set()

Kirben pointed out that there were more loyalty rating events tied
to this opcode than to off_loadVideo(). I didn't notice this
myself since the video loading was so much easier to spot in the
script dump. It's a pity there doesn't seem to be any one opcode
that covers all of the cases.