Simplifications and clarification to update callback handling in the
OP_Delete and OP_Insert opcodes.

FossilOrigin-Name: 47887ef89ed60ddb869d65e0957c1c4b2115f169
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 8500403..d789cc0 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2927,9 +2927,6 @@
 
 /*
 ** Bitfield flags for P5 value in various opcodes.
-**
-** Note that the values for ISNOOP and LENGTHARG are the same.  But as 
-** those bits are never used on the same opcode, the overlap is harmless.
 */
 #define OPFLAG_NCHANGE       0x01    /* OP_Insert: Set to update db->nChange */
                                      /* Also used in P2 (not P5) of OP_Delete */
@@ -2938,7 +2935,9 @@
 #define OPFLAG_ISUPDATE      0x04    /* This OP_Insert is an sql UPDATE */
 #define OPFLAG_APPEND        0x08    /* This is likely to be an append */
 #define OPFLAG_USESEEKRESULT 0x10    /* Try to avoid a seek in BtreeInsert() */
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
 #define OPFLAG_ISNOOP        0x40    /* OP_Delete does pre-update-hook only */
+#endif
 #define OPFLAG_LENGTHARG     0x40    /* OP_Column only used for length() */
 #define OPFLAG_TYPEOFARG     0x80    /* OP_Column only used for typeof() */
 #define OPFLAG_BULKCSR       0x01    /* OP_Open** used to open bulk cursor */