Script to add auxiliary mapping tables.

The script adds one table by subset previously added to the database and
maps all terms to the closest term within that subset.  The tables are
named "aux_XX_YY_map" where "XX" is the ontology ("GO" or "SO"), and
"YY" is the subset name (e.g., "goslim_goa").

The schema for each of the subset map tables is simply as follows:

  +----------------+------------------+------+-----+---------+-------+
  | Field          | Type             | Null | Key | Default | Extra |
  +----------------+------------------+------+-----+---------+-------+
  | term_id        | int(10) unsigned | NO   | PRI | NULL    |       |
  | subset_term_id | int(10) unsigned | NO   | PRI | NULL    |       |
  +----------------+------------------+------+-----+---------+-------+

... where both fields refers into the 'term' table.