Minor TOAST patch (regression test and source comment)

Hi all,

The following small patch provides a couple of minor updates (against
CVS HEAD):

Amended "strings" regression test. TOAST tests now insert two values
with storage set to "external", to exercise properly the TOAST slice
routines which fetch only a subset of the chunks.

Changed now-misleading comment on AlterTableCreateToastTable in
tablecmds.c, because both columns of the index on a toast table are now
used.

Regards

John
--
John Gray
Azuli IT
www.azuli.co.uk