Re: refactor AlterDomainAddConstraint (alter domain add constraint)

hi.
ALTER DOMAIN ADD CONSTRAINT syntax more simple than CREATE DOMAIN.
So in gram.y, I changed DomainConstraintElem to the following:

DomainConstraintElem:
CHECK '(' a_expr ')'
{
Constraint *n = makeNode(Constraint);
n->contype = CONSTR_CHECK;
n->location = @1;
n->raw_expr = $3;
n->cooked_expr = NULL;
n->initially_valid = true;
$$ = (Node *) n;
}
| CHECK '(' a_expr ')' NOT VALID
{
Constraint *n = makeNode(Constraint);
n->contype = CONSTR_CHECK;
n->location = @1;
n->raw_expr = $3;
n->cooked_expr = NULL;
n->initially_valid = false;
n->skip_validation = true;
$$ = (Node *) n;
}
| NOT NULL_P
{
Constraint *n = makeNode(Constraint);
n->contype = CONSTR_NOTNULL;
n->location = @1;
n->keys = list_make1(makeString("value"));
n->initially_valid = true;
$$ = (Node *) n;
}

Now everything is the same as alter domain synopsis.
It all looks so simple.