- Tell the programs executed by mysql_upgrade to only read
  from the defaults file generated by msyql_upgrade
 - Fix memory leaks


client/mysql_upgrade.c:
  - Always generate defaults file used for the programs executed
    by mysql_upgrade.
  - Set the executed programs to read options _only_ from the
    generated defaults file 
  - Add DBUG printouts
  - Add comments
  - Fix memory leaks
  - Change one 'my_delete'(delete a file) to 'my_free'(free memory)
  - Free memory allocated by 'load_default'