move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/transport/once_close.go

@@ -0,0 +1,21 @@
+package transport
+
+import (
+	"net"
+	"sync"
+)
+
+// onceCloseListener wraps a net.Listener, protecting it from
+// multiple Close calls.
+type onceCloseListener struct {
+	net.Listener
+	once sync.Once
+	err  error
+}
+
+func (o *onceCloseListener) Close() error {
+	o.once.Do(func() {
+		o.err = o.Listener.Close()
+	})
+	return o.err
+}