Re: Aggregate ORDER BY patch

Updated version of the aggregate order by patch.

Includes docs + regression tests all in the same patch.

Changes:

  - removed SortGroupClause.implicit as per review comments,
    replacing it with separate lists for Aggref.aggorder and
    Aggref.aggdistinct.

  - Refactored in order to move the bulk of the new parse code
    out of ParseFuncOrColumn which was already quite big enough,
    into parse_agg.c

  - fixed a bug with incorrect deparse in ruleutils (and added a
    bunch of regression tests for deparsing and view usage)

  - added some comments

--
Andrew (irc:RhodiumToad)