Make sure the dispose() method of any schema import tool is ALWAYS
called, so also in the case of an exception (this was not the case,
resulting in connections not being closed).
Fix error in element synonym comment list query; this query is created
and executed for each element that has an INDEXED BY clause (which we
should eliminate in the future for performance reasons).
Improve the performance of the element list query by replacing the 2
subqueries by a list of RCDSYN-079 dbkeys.  Further improvements should
be made to also filter the SR-036 occurrences traversed.

On dictionaries with a significant amount of records, record synonyms
and elements, the element list query just didn't perform and would take
forever to complete, while consuming excessive CPU time.