Fix possible endian issues with MsnNotificationConnectionP15::loginSucceeded()

[diederik]

The architecture issues in MsnNotificationConnectionP15::loginSucceeded() likely have a different issue as well for Big Endian / Low Endian systems.

This can be fixed by using QDataStream or P2PMessage::insertBytes(). For QDataStream, you can set the required endianness. Unforfortunatey it's not completely raw, so after setting the proper Qt version you need to check if it doesn't add padding itself.