Add asserts as evidence that all FK constraints are either immediate or
deferred.

FossilOrigin-Name: 634ef4fc9f4051245b38f558bb1c733031548c2f
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 03ff1be..2675f44 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1289,6 +1289,7 @@
   FKey *pNextTo;    /* Next foreign key on table named zTo */
   FKey *pPrevTo;    /* Previous foreign key on table named zTo */
   int nCol;         /* Number of columns in this key */
+  /* EV: R-30323-21917 */
   u8 isDeferred;    /* True if constraint checking is deferred till COMMIT */
   u8 aAction[2];          /* ON DELETE and ON UPDATE actions, respectively */
   Trigger *apTrigger[2];  /* Triggers for aAction[] actions */