Fix building with SQLITE_OMIT_FOREIGN_KEY defined.

FossilOrigin-Name: e93d2c49a44af994ff10cc9cc7eafacd5a4f73ab
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 4b7bdf5..4a28ebc 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -4186,6 +4186,7 @@
   #define sqlite3FkDropTable(a,b,c)
   #define sqlite3FkOldmask(a,b)         0
   #define sqlite3FkRequired(a,b,c,d)    0
+  #define sqlite3FkReferences(a)        0
 #endif
 #ifndef SQLITE_OMIT_FOREIGN_KEY
   void sqlite3FkDelete(sqlite3 *, Table*);