The oracle will not register nonsense/useless relations, (basically X op 
X).  Symbolically,  x == x  is implied, and x != x, x< x, etc are all 
nonsense.

Now that we are using class value_relation in a couple of other places, 
it shouldn't either.

Bootstrapped on  x86_64-pc-linux-gnu with no regressions. Pushed.

Andrew