Fixes for a couple of resource leaks

Hi all,

Coverity is pointing out a couple of resource leaks:
- In DropReplicationSlot(at)streamutil(dot)c, query is leaked.
- In getTransforms(at)pg_dump(dot)c, the alloced result of get_language_name is
not free'd. Other code paths calling this routine do the job.
- In libpqGetCurrentXlogInsertLocation(at)libpq_fetch(dot)c (pg_rewind), the value
"val" returned by run_simple_query should be free'd. Other code paths do so.
- In libpqProcessFileList(at)libpq_fetch(dot)c, a call to PQclear is missing for a
query result.
- In vacuum_one_database(at)vacuumdb(dot)c, a call to PQclear is missing.
Attached is a patch to address all those things. Backpatches would be good
to have as well.
Regards,
--
Michael