database out of memory error for LYBUNT, SYBUNT reports - use temp table for more efficient query

In some environments, SYBUNT and LYBUNT reports result in database out of memory errors, so no report results are generated. One possibility to reduce the memory usage, which causes the reports work in my case, is to change the queries from using a subqueries to using temporary tables, instead.

See the forum for details: http://forum.civicrm.org/index.php/topic,12098.0.html