Omit all use of Expr nodes for TK_AS, as those nodes no longer served a useful
purpose and in fact interferred with the query planner.

FossilOrigin-Name: 7ab0b258eabfcfb7f1b0bd1b12e166d2f267823d
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 69315ed..89b3d79 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2135,6 +2135,7 @@
 #define EP_ConstFunc 0x080000 /* A SQLITE_FUNC_CONSTANT or _SLOCHNG function */
 #define EP_CanBeNull 0x100000 /* Can be null despite NOT NULL constraint */
 #define EP_Subquery  0x200000 /* Tree contains a TK_SELECT operator */
+#define EP_Alias     0x400000 /* Is an alias for a result set column */
 
 /*
 ** Combinations of two or more EP_* flags