Document that all errors from RPCs are status errors (#1782)

stream.go

@@ -50,6 +50,8 @@ type StreamDesc struct {
 }
 
 // Stream defines the common interface a client or server stream has to satisfy.
+//
+// All errors returned from Stream are compatible with the status package.
 type Stream interface {
 	// Context returns the context for this stream.
 	Context() context.Context