[patch] some PQExpBuffer are not destroyed in pg_dump

Hi al

In getDefaultACLs function, some PQExpBuffer are not destroy

File: src/bin/pg_dump/pg_dump.c
DefaultACLInfo *
getDefaultACLs(Archive *fout, int *numDefaultACLs)
{
......
	if (fout->remoteVersion >= 90600)
	{
		PQExpBuffer acl_subquery = createPQExpBuffer();       // *** acl_subquery not destroyed ***
		PQExpBuffer racl_subquery = createPQExpBuffer();      // *** racl_subquery not destroyed ***
		PQExpBuffer initacl_subquery = createPQExpBuffer();   // *** initacl_subquery not destroyed ***
		PQExpBuffer initracl_subquery = createPQExpBuffer();  // *** initracl_subquery not destroyed ***

		buildACLQueries(acl_subquery, racl_subquery, initacl_subquery,
						initracl_subquery, "defaclacl", "defaclrole",
						"CASE WHEN defaclobjtype = 'S' THEN 's' ELSE defaclobjtype END::\"char\"",
						dopt->binary_upgrade);

		appendPQExpBuffer(query, "SELECT d.oid, d.tableoid, "
						  "(%s d.defaclrole) AS defaclrole, "
						  "d.defaclnamespace, "
						  "d.defaclobjtype, "
						  "%s AS defaclacl, "
						  "%s AS rdefaclacl, "
						  "%s AS initdefaclacl, "
						  "%s AS initrdefaclacl "
						  "FROM pg_default_acl d "
						  "LEFT JOIN pg_init_privs pip ON "
						  "(d.oid = pip.objoid "
						  "AND pip.classoid = 'pg_default_acl'::regclass "
						  "AND pip.objsubid = 0) ",
						  username_subquery,
						  acl_subquery->data,
						  racl_subquery->data,
						  initacl_subquery->data,
						  initracl_subquery->data);
	}
......

Here is a patch.

Best Regards!