This wasn't stated anywhere, and it's perhaps not that obvious,
since we get questions about it from time to time.  Also undocumented
was that the parser actually translates these into operators.

Discussion: https://postgr.es/m/CAFj8pRBkvZ71BqGKZnBBG4=0cKG+s50Dy+DYmrizUKEpAtdc+w@mail.gmail.com