Add missing PQclear(), and comment touchups.
Add missing PQclear(), and comment touchups.

Fixed by Daniele: PQclear already committed, only left the comments touchups.

reorg/pg_reorg,reorg/pg_reorg,ossc-db/pg_reorg,reorg/pg_repack,mr-mustash/pg_repack,reorg/pg_repack,bwtakacy/pg_repack