[MONDRIAN-1587] Drillthrough SQL is invalid on hsqldb. SQL formerly included redundant parentheses in cases where drillthrough was generating a single field IN list, for example "field" IN ( ('item1'), ('item2' ).
 Merged from e411d5b
Merge pull request #87 from mkambol/lag-1587

 [MONDRIAN-1587] Drillthrough SQL is invalid on hsqldb. SQL formerly inc...