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/mtproto/handle_gzip.go

@@ -0,0 +1,24 @@
+package mtproto
+
+import (
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/proto"
+)
+
+func gzip(b *bin.Buffer) (*bin.Buffer, error) {
+	var content proto.GZIP
+	if err := content.Decode(b); err != nil {
+		return nil, errors.Wrap(err, "decode")
+	}
+	return &bin.Buffer{Buf: content.Data}, nil
+}
+
+func (c *Conn) handleGZIP(msgID int64, b *bin.Buffer) error {
+	content, err := gzip(b)
+	if err != nil {
+		return errors.Wrap(err, "unzip")
+	}
+	return c.handleMessage(msgID, content)
+}