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/query/internal/genutil/func.go

@@ -0,0 +1,55 @@
+package genutil
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/go/packages"
+)
+
+// Func is a function representation.
+type Func struct {
+	Sig  *types.Signature
+	Decl *types.Func
+}
+
+// Results returns function results.
+func (f Func) Results() *types.Tuple {
+	return f.Sig.Results()
+}
+
+// Args returns function arguments.
+func (f Func) Args() *types.Tuple {
+	return f.Sig.Params()
+}
+
+// Funcs collects all function from package using given filter.
+// Parameter keep may be nil.
+func Funcs(pkg *packages.Package, keep func(f Func) bool) []Func {
+	var r []Func
+
+	for _, def := range pkg.TypesInfo.Defs {
+		if def == nil {
+			continue
+		}
+
+		f, ok := def.(*types.Func)
+		if !ok {
+			continue
+		}
+
+		sig, ok := f.Type().(*types.Signature)
+		if !ok {
+			continue
+		}
+		repr := Func{
+			Sig:  sig,
+			Decl: f,
+		}
+
+		if keep(repr) {
+			r = append(r, repr)
+		}
+	}
+
+	return r
+}