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/bin/pool_test.go

@@ -0,0 +1,24 @@
+package bin
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPool_GetSize(t *testing.T) {
+	sizes := []int{0, 1024}
+
+	for _, size := range sizes {
+		a := require.New(t)
+		p := NewPool(size)
+
+		b := p.Get()
+		a.Empty(b.Buf)
+		p.Put(b)
+
+		b = p.GetSize(1024)
+		a.Len(b.Buf, 1024)
+		p.Put(b)
+	}
+}