Adding upstream version 7.1.3.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tests/fixtures/optimizer/eliminate_ctes.sql

@@ -0,0 +1,48 @@
+# title: CTE
+WITH q AS (
+  SELECT
+    a
+  FROM x
+)
+SELECT
+  a
+FROM x;
+SELECT
+  a
+FROM x;
+
+# title: Nested CTE
+SELECT
+  a
+FROM (
+  WITH q AS (
+    SELECT
+      a
+    FROM x
+  )
+  SELECT a FROM x
+);
+SELECT
+  a
+FROM (
+  SELECT
+    a
+  FROM x
+);
+
+# title: Chained CTE
+WITH q AS (
+  SELECT
+    a
+  FROM x
+), r AS (
+  SELECT
+    a
+  FROM q
+)
+SELECT
+  a
+FROM x;
+SELECT
+  a
+FROM x;