add argument type to postgres_fdw docs

[Shinya11.Kato]

Hi,

I add argument type to postgres-fdw parameters in postgres-fdw.sgml.
I think this change is kind. Do you think?

Regards,
Shinya Kato

add_argument_type_to_postgres-fdw_docs.patch
Description: add_argument_type_to_postgres-fdw_docs.patch