Minor cleanups of the compound-subquery flattening logic.  New test cases
added for joins the compound subquery.

FossilOrigin-Name: 5061d85ff934db3c217c97acbbbed3286d9e02aa
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 6266a9c..8613d86 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1772,7 +1772,7 @@
     char *zSpan;           /* Original text of the expression */
     u8 sortOrder;          /* 1 for DESC or 0 for ASC */
     u8 done;               /* A flag to indicate when processing is finished */
-    u16 iCol;              /* For ORDER BY, column number in result set */
+    u16 iOrderByCol;       /* For ORDER BY, column number in result set */
     u16 iAlias;            /* Index into Parse.aAlias[] for zName */
   } *a;                  /* One entry for each expression */
 };