Add a new optimizer disabling bit to close off the exists-to-in optimization,

for testing purposes.

FossilOrigin-Name: a80c9a076d31729282004ca372913c9fdbfb6e74711fbb8c5dc12ee0ecba2b87

src/sqliteInt.h

@@ -1721,6 +1721,7 @@ struct sqlite3 {
 #define SQLITE_SkipScan       0x00004000 /* Skip-scans */
 #define SQLITE_PropagateConst 0x00008000 /* The constant propagation opt */
 #define SQLITE_MinMaxOpt      0x00010000 /* The min/max optimization */
+#define SQLITE_ExistsToIN     0x00020000 /* The EXISTS-to-IN optimization */
 #define SQLITE_AllOpts        0xffffffff /* All optimizations */
 
 /*