Predicate eqOpWithSwapAndNegate

Holds if cmp is an equality operation (== or !=) with fully-converted children a and b, isEQ is true if cmp is an == operation and false if it is an != operation, and the result is branch.

This allows for the comparison to be either as written, or with its arguments reversed; for example, if cmp is x == 5 then eqOpWithSwapAndNegate(cmp, x, 5, true, true), eqOpWithSwapAndNegate(cmp, 5, x, true, true), eqOpWithSwapAndNegate(cmp, x, 5, false, false) and eqOpWithSwapAndNegate(cmp, 5, x, false, false) hold.