Change UserID to int64

[Syfaro]

As per Telegram docs, user IDs will potentially contain up to 52 significant bits.

After one of the upcoming Bot API updates, some user identifiers will become bigger than 2^31 - 1 and it will be no longer possible to store them in a signed 32-bit integer type. User identifiers will have up to 52 significant bits, so a 64-bit integer or double-precision float type would still be safe for storing them. Please make sure that your code can correctly handle such user identifiers.