event: deprecate TypeMux and related types

The Subscription type is gone, all uses are replaced by
*TypeMuxSubscription. This change is prep-work for the
introduction of the new Subscription type in a later commit.

   gorename -from '"github.com/ethereum/go-ethereum/event"::Event' -to TypeMuxEvent
   gorename -from '"github.com/ethereum/go-ethereum/event"::muxsub' -to TypeMuxSubscription
   gofmt -w -r 'Subscription -> *TypeMuxSubscription' ./event/*.go
   find . -name '*.go' -and -not -regex '\./vendor/.*' \| xargs gofmt -w -r 'event.Subscription -> *event.TypeMuxSubscription'

eth/handler.go

@@ -78,8 +78,8 @@ type ProtocolManager struct {
 	SubProtocols []p2p.Protocol
 
 	eventMux      *event.TypeMux
-	txSub         event.Subscription
-	minedBlockSub event.Subscription
+	txSub         *event.TypeMuxSubscription
+	minedBlockSub *event.TypeMuxSubscription
 
 	// channels for fetcher, syncer, txsyncLoop
 	newPeerCh   chan *peer