core, miner: add PendingStateEvent to track non-log updates

core/events.go

@@ -35,6 +35,9 @@ type PendingLogsEvent struct {
 	Logs vm.Logs
 }
 
+// PendingStateEvent is posted pre mining and notifies of pending state changes.
+type PendingStateEvent struct{}
+
 // NewBlockEvent is posted when a block has been imported.
 type NewBlockEvent struct{ Block *types.Block }