pg_largeobject and toast

hi,

what's a supposed way for a user to create a toast table?
the comment in include/storage/large_object.h
("unless the user creates a toast-table for pg_largeobject...")
made me think there's a way, but i couldn't find one.

currently, the pg_largeobject table is created without a toast table
while it has a column with the EXTENDED storage parameter and
needs_toast_table() would return true for it.
so, a unrelated modification like the following will create
a toast table for it.  is it considered a bug?

    alter table pg_largeobject alter column data set statistics -1;

(it's convenient for me as it doesn't require allow_system_table_mods=on,
but...)

YAMAMOTO Takashi