RawTreeSet with sometimes use Java .equals() instead of the specified comperator

[krame505]

I discovered when trying to make a Set<Decorated Name> with a compirator of \ n1 n2 -> compare(n1.name, n2.name), that removeAll and difference will sometimes return the wrong result. It seems that the native .equals() method is being used, instead of the specified comparison function. This is not an issue with primitive types which have a Java .equals() matching the Eq/Ord instance, but this is a problem for types with custom a Eq/Ord.

Not sure if there is a good fix for this without impacting performance (which is the point of this library.)