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

FossilOrigin-Name: 5061d85ff934db3c217c97acbbbed3286d9e02aa
diff --git a/src/resolve.c b/src/resolve.c
index 6d857f0..3da4813 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -799,7 +799,7 @@
         pE->pColl = pColl;
         pE->flags |= EP_IntValue | flags;
         pE->u.iValue = iCol;
-        pItem->iCol = (u16)iCol;
+        pItem->iOrderByCol = (u16)iCol;
         pItem->done = 1;
       }else{
         moreToDo = 1;
@@ -848,12 +848,12 @@
   pEList = pSelect->pEList;
   assert( pEList!=0 );  /* sqlite3SelectNew() guarantees this */
   for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
-    if( pItem->iCol ){
-      if( pItem->iCol>pEList->nExpr ){
+    if( pItem->iOrderByCol ){
+      if( pItem->iOrderByCol>pEList->nExpr ){
         resolveOutOfRangeError(pParse, zType, i+1, pEList->nExpr);
         return 1;
       }
-      resolveAlias(pParse, pEList, pItem->iCol-1, pItem->pExpr, zType);
+      resolveAlias(pParse, pEList, pItem->iOrderByCol-1, pItem->pExpr, zType);
     }
   }
   return 0;
@@ -900,7 +900,7 @@
       ** a copy of the iCol-th result-set column.  The subsequent call to
       ** sqlite3ResolveOrderGroupBy() will convert the expression to a
       ** copy of the iCol-th result-set expression. */
-      pItem->iCol = (u16)iCol;
+      pItem->iOrderByCol = (u16)iCol;
       continue;
     }
     if( sqlite3ExprIsInteger(pE, &iCol) ){
@@ -911,12 +911,12 @@
         resolveOutOfRangeError(pParse, zType, i+1, nResult);
         return 1;
       }
-      pItem->iCol = (u16)iCol;
+      pItem->iOrderByCol = (u16)iCol;
       continue;
     }
 
     /* Otherwise, treat the ORDER BY term as an ordinary expression */
-    pItem->iCol = 0;
+    pItem->iOrderByCol = 0;
     if( sqlite3ResolveExprNames(pNC, pE) ){
       return 1;
     }