Bugged code patched, but not in the optimal way.

Bugged code patched, but not in the optimal way.
The problem is that in two different interpretations a symbol id can be
interpreted as dsc in different locations. Using the previous code it
happened that every interpretation was pruned out since a symbol id occurred
twice (in different locations) in an/every interpretation. Now the couples
(loc,id) are considered for disambiguating between the two interpretations.
However, this way we hide information to the user (what other occurrences of
the same symbol are given the same interpretation).