Aggregate expression syntax

Hi all,

Looking at the syntax for aggregate expressions in the docs, it seems the
first three forms could perhaps be merged since the ALL and DISTINCT
keywords are effectively optional.

Currently:

aggregate_name (expression [ , ... ] [ order_by_clause ] ) [ FILTER ( WHERE
filter_clause ) ]
aggregate_name (ALL expression [ , ... ] [ order_by_clause ] ) [ FILTER (
WHERE filter_clause ) ]
aggregate_name (DISTINCT expression [ , ... ] [ order_by_clause ] ) [
FILTER ( WHERE filter_clause ) ]

Proposed:

aggregate_name ( [ ALL | DISTINCT ] expression [ , ... ] [ order_by_clause
] ) [ FILTER ( WHERE filter_clause ) ]

I've also found a precedent for this on the SELECT statement page:

[ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ]

Patch attached with the proposed change.

Opinions?

Thom