Allow the use of parenthesis in CREATE TABLE AS (...)

Author: asfernandes

doc/sql.extensions/README.create_table_as_query.md

@@ -5,7 +5,7 @@ Tables may be created from a query result using the following syntax:
 ```sql
 CREATE [{GLOBAL | LOCAL} TEMPORARY] TABLE [IF NOT EXISTS] <table name>
   [ (<column name> [, <column name> ...]) ]
-  AS <query expression>
+  AS { (<query expression>) | <query expression> }
   [WITH [NO] DATA]
   [ON COMMIT {DELETE | PRESERVE} ROWS]
 ```
@@ -67,6 +67,12 @@ CREATE LOCAL TEMPORARY TABLE tx_work AS
   SELECT emp_no, salary
     FROM employee
   WITH NO DATA;
+
+CREATE TABLE high_salary AS
+  (WITH avg_salary AS (SELECT AVG(salary) AS avg_salary FROM employee)
+   SELECT e.emp_no, e.salary
+     FROM employee e, avg_salary a
+     WHERE e.salary > a.avg_salary);
 ```
 
 ## ISQL behavior

src/dsql/parse-conflicts.txt

@@ -1 +1 @@
-152 shift/reduce conflicts, 7 reduce/reduce conflicts.
+153 shift/reduce conflicts, 7 reduce/reduce conflicts.

src/dsql/parse.y

@@ -2441,6 +2441,15 @@ table_as_query_clause
 			node->withData = $5;
 			$$ = node;
 		}
+	| simple_table_name column_parens_opt AS '(' select_expr ')' with_data_opt
+		{
+			const auto node = newNode<CreateRelationNode>($1);
+			node->queryColumns = $2;
+			node->querySelectExpr = $5;
+			node->querySource = makeParseStr(YYPOSNARG(5), YYPOSNARG(5));
+			node->withData = $7;
+			$$ = node;
+		}
 	;
 
 %type <createRelationNode> table_clause