This bugfix makes sure that from a set of symbols with the same
address, only the first one gets imported.
After an assessment whether analysis scripts can deal with multiple
symbols at the same address, an import of all symbols should be made
possible in the future. This will also require to relax the
primary-key constraint of the `symbols' table.
Change-Id: I61c4ddb1af1556d44eab54e53eaa3d0fc20de7c1
68229afa84