Optionally enforce different handle values for different variable names in query answers

[andre-senna]

For instance, in a query like this one:

AND
    LINK_TEMPLATE Expression 3 
        NODE Symbol EVALUATION 
        LINK_TEMPLATE Expression 2
            NODE Symbol PREDICATE
            VARIABLE V1
        LINK_TEMPLATE Expression 2
            NODE Symbol CONCEPT
            VARIABLE V2
    LINK_TEMPLATE Expression 3 
        NODE Symbol EVALUATION 
        LINK_TEMPLATE Expression 2
            NODE Symbol PREDICATE
            VARIABLE V3
        LINK_TEMPLATE Expression 2
            NODE Symbol CONCEPT
            VARIABLE V4

The caller can, optionally, request that the mappings for V1, V2, V3 and V4 NEED to be different in any QueryAnswer. I.e., if V1 is assigned to a given handle H1, none of the other variables can be assigned to the same H1.