- Add sql_table_name which keeps track of the table name being updated.

- Add sql_table_name which keeps track of the table name being updated.
  This is needed by PostgreSQL.  macro does nothing under MySQL/SQLite
- Add table_name to the PostgreSQL db structure
- remove LastID from the PostgreSQL structure as it is no longer needed
- ensure sql_num_rows, sql_affected_rows, and sql_num_fields return
  unsigned values