Proposal : composite type not null constraints

I would like to propose extending composite types with constraints.
Currently there is a preliminar patch for not null constraints.

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Changes :
-Use the parser from create table to get the constraints
'OptTableElementList' instead of 'OptTableFuncElementList'.
- Add a new transformation transformCompositeTypeStmt similar to
transformCreateStmt to add constraint informations to stmt.
- Implement a recursive notnull check when a type is composite
==
Features enabled :
- Enable not null in parser for
create type tyname AS ( a type NOT NULL )
- Check for null in rowtypes

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Wesley S. Massuda