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/tdsync/reset_ready.go

@@ -0,0 +1,41 @@
+package tdsync
+
+import "sync"
+
+// ResetReady is like Ready, but can be Reset.
+type ResetReady struct {
+	ready Ready
+	lock  sync.Mutex
+}
+
+// NewResetReady creates new ResetReady.
+func NewResetReady() *ResetReady {
+	return &ResetReady{
+		ready: Ready{
+			wait: make(chan struct{}),
+		},
+	}
+}
+
+// Reset resets underlying Ready.
+func (r *ResetReady) Reset() {
+	r.lock.Lock()
+	r.ready.Signal()
+	r.ready.reset()
+	r.lock.Unlock()
+}
+
+// Signal sends ready signal.
+// Can be called multiple times.
+func (r *ResetReady) Signal() {
+	r.lock.Lock()
+	r.ready.Signal()
+	r.lock.Unlock()
+}
+
+// Ready returns waiting channel.
+func (r *ResetReady) Ready() <-chan struct{} {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	return r.ready.Ready()
+}