wl2k: Utilize the new Flusher and TxBuffer interfaces in writeCompressed.
wl2k: Utilize the new Flusher and TxBuffer interfaces in writeCompressed.

This enables us to block until the whole message has been transmitted over the air,
as well as giving more reliable transfer status updates.

It will also make it easier to implement Robust modes when not transferring messages.

LA5NTA/wl2k-go,LA5NTA/wl2k-go