New version of GENERATED/IDENTITY, was Re: parser dilemma

Hi,

here's the patch with the modifications suggested by Tom Lane.
The postfix rule was deleted from b_expr and the reverse parsing
in ruleutils.c::get_oper_expr() always puts parentheses around
postfix operators.

Other changes:
- OVERRIDING SYSTEM VALUE in COPY can appear
   at any place in the option list.
- pg_dump was modified accordingly
- \copy built-in in psql now also accepts OVERRIDING SYSTEM VALUE
- documentation and testcase updates

Please, review.

Best regards,
Zoltán Böszörményi

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Zoltán Böszörményi
Cybertec Geschwinde & Schönig GmbH
http://www.postgresql.at/