Fix assorted memory leaks.

Per Coverity (not that any of these are so non-obvious that they should not
have been caught before commit).  The extent of leakage is probably minor
to unnoticeable, but a leak is a leak.  Back-patch as necessary.

Michael Paquier

src/bin/pg_dump/pg_dump.c

@@ -14007,6 +14007,7 @@ getExtensionMembership(ExtensionInfo extinfo[], int numExtensions)
 		addObjectDependency(&contable->dataObj->dobj,
 							reftable->dataObj->dobj.dumpId);
 	}
+	PQclear(res);
 	destroyPQExpBuffer(query);
 }