Fix a defect in the query-flattener optimization identified by

ticket [8f157e8010b22af0]. This fix is associated with CVE-2020-15358.

FossilOrigin-Name: 9e001b635f3cff672e591204ab90deefe01baaefe64ff121bd2c32edd2d03675

src/sqliteInt.h

@@ -2888,6 +2888,7 @@ struct Select {
 #define SF_Converted      0x10000  /* By convertCompoundSelectToSubquery() */
 #define SF_IncludeHidden  0x20000  /* Include hidden columns in output */
 #define SF_ComplexResult  0x40000  /* Result contains subquery or function */
+#define SF_NoopOrderBy   0x0400000 /* ORDER BY is ignored for this query */
 
 /*
 ** The results of a SELECT can be distributed in several ways, as defined