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/fileid/rle.go

@@ -0,0 +1,39 @@
+package fileid
+
+import "bytes"
+
+func rleEncode(s []byte) (r []byte) {
+	var count byte
+	for _, cur := range s {
+		if cur == 0 {
+			count++
+			continue
+		}
+
+		if count > 0 {
+			r = append(r, 0, count)
+			count = 0
+		}
+		r = append(r, cur)
+	}
+	if count > 0 {
+		r = append(r, 0, count)
+	}
+
+	return r
+}
+
+func rleDecode(s []byte) (r []byte) {
+	var last []byte
+	for _, cur := range s {
+		if string(last) == string(rune(0)) {
+			r = append(r, bytes.Repeat(last, int(cur))...)
+			last = nil
+		} else {
+			r = append(r, last...)
+			last = []byte{cur}
+		}
+	}
+	r = append(r, last...)
+	return r
+}