ALTER FOREIGN TABLE: unsupported features

Hi,

I noticed that ALTER FOREIGN TABLE document mentions unsupported features:

  - table inheritance
  - oid system column
  - CHECK constraint
  - per-column FDW options

http://developer.postgresql.org/pgdocs/postgres/sql-alterforeigntable.html

These features have been proposed once, but were not committed.  On the
other hand, CREATE FOREIGN TABLE document seems fine as is, it doesn't
mention any unsupported feature.

Please find attached a patch for the document correction.  The patch
also replaces the phrase "table" with "foreign table" for wording
consistency.

Regards,
--
Shigeru Hanada