Fix memory arrangement of tsquery after removing stop words. It causes

a unused memory holes in tsquery.

Per report by Richard Huxton <dev@archonet.com>.

It was working well because in fact tsquery->size is not used for any
kind of operation except comparing tsqueries. So, in HEAD it's enough to
fix to_tsquery function, but for previous version it's needed to
remove optimization in CompareTSQ to prevent requirement of renew all
stored tsquery.