Implement stats.getMessagePublicForwards

[aykutalparslan]

Obtains a list of messages, indicating to which other public channels was a channel message forwarded. Will return a list of messages with peer_id equal to the public channel to which this message was forwarded.

messages.messages#8c718e87 messages:Vector<Message> chats:Vector<Chat> users:Vector<User> = messages.Messages; messages.messagesSlice#3a54685e flags:# inexact:flags.1?true count:int next_rate:flags.0?int offset_id_offset:flags.2?int messages:Vector<Message> chats:Vector<Chat> users:Vector<User> = messages.Messages; messages.channelMessages#64479808 flags:# inexact:flags.1?true pts:int count:int offset_id_offset:flags.2?int messages:Vector<Message> chats:Vector<Chat> users:Vector<User> = messages.Messages; messages.messagesNotModified#74535f21 count:int = messages.Messages; ---functions--- stats.getMessagePublicForwards#5630281b channel:InputChannel msg_id:int offset_rate:int offset_peer:InputPeer offset_id:int limit:int = messages.Messages;