add parsing support for OUT and INOUT argmode for routines

[jennifersp]

Aggregate only allows IN and VARIADIC argument modes. Routines including functions and procedures allows IN, VARIADIC, OUT and INOUT modes. The parser will allow OUT and INOUT for aggregates, so TODO there needs a check during ast evaluation/conversion for these modes in aggregate statements.

• small fix for supporting SETOF modifier option for CREATE FUNCTION statement.
• small fix for supporting db.aggregate_name syntax for AGGREGATE statements.

[Hydrocharged]

LGTM!