pgsql: Add/ cleanup: < * %Disallow changing default expression of a

Log Message:
-----------
Add/ cleanup:

< * %Disallow changing default expression of a SERIAL column?

* %Disallow changing DEFAULT expression of a SERIAL column?

472a473,476

* Add DEFAULT .. AS OWNER so permission checks are done as the table
owner

This would be useful for SERIAL nextval() calls and CHECK constraints.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1820 -> r1.1821)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1820&amp;r2=1.1821)
pgsql/doc/src/FAQ:
TODO.html (r1.323 -> r1.324)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.323&amp;r2=1.324)