Predicate relOpWithSwapAndNegate

Holds if rel is a comparison operation (<, >, <= or >=) with fully-converted children a and b, described by dir and strict, with result branch.

This allows for the relation to be either as written, or with its arguments reversed; for example, if rel is x < 5 then relOpWithSwapAndNegate(rel, x, 5, Lesser(), Strict(), true), relOpWithSwapAndNegate(rel, 5, x, Greater(), Strict(), true), relOpWithSwapAndNegate(rel, x, 5, Greater(), Nonstrict(), false) and relOpWithSwapAndNegate(rel, 5, x, Lesser(), Nonstrict(), false) hold.