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/telegram/updates/gap_buffer.go

@@ -0,0 +1,54 @@
+package updates
+
+import "go.uber.org/zap/zapcore"
+
+type gap struct {
+	from, to int
+}
+
+type gapBuffer struct {
+	gaps []gap
+}
+
+func (b gapBuffer) Has() bool { return len(b.gaps) > 0 }
+
+func (b *gapBuffer) Clear() { b.gaps = make([]gap, 0, 1) }
+
+func (b *gapBuffer) Enable(from, to int) {
+	if len(b.gaps) > 0 {
+		panic("unreachable")
+	}
+
+	b.gaps = append(b.gaps, gap{from, to})
+}
+
+func (b *gapBuffer) Consume(u update) (accepted bool) {
+	for i, g := range b.gaps {
+		if g.from <= u.start() && g.to >= u.end() {
+			if g.from < u.start() {
+				b.gaps = append(b.gaps, gap{from: g.from, to: u.start()})
+			}
+			if g.to > u.end() {
+				b.gaps = append(b.gaps, gap{from: u.end(), to: g.to})
+			}
+
+			b.gaps = append(b.gaps[:i], b.gaps[i+1:]...)
+			return true
+		}
+	}
+
+	return false
+}
+
+func (b gapBuffer) MarshalLogArray(e zapcore.ArrayEncoder) error {
+	for _, g := range b.gaps {
+		if err := e.AppendObject(zapcore.ObjectMarshalerFunc(func(e zapcore.ObjectEncoder) error {
+			e.AddInt("from", g.from)
+			e.AddInt("to", g.to)
+			return nil
+		})); err != nil {
+			return err
+		}
+	}
+	return nil
+}