How to simplify result from domain function

[Albert Chan]

The bug probably not from simplify, but x≠3

XCas> purge(x)
XCas> x >= 3      // returns x ≥ 3, as expected
XCas> x != 3       // returns true ???

XCas> [(x <= -3), (x >= 3) and (x != 3)]       // dropped "and true", returns [x <= -3, x >= 3]