Acknowledge client awareness level.

This message is supported as of server revision 4.

Client awareness level:

This is a value used by revision 4 servers to add functionality but keep backwards compatibility. Fields marked with awl: 1 in this documentation require the client to send this message with Client awareness level set to 0x01 for them to be received in server to client messages.

• 0x00: awl of 0 (default).
• 0x01: awl of 1.

Clients should continue to parse assuming an old awl until they receive this message as confirmation of their requested change.