support for Reconnect pseudo-UAM

[rdmark]

the Reconnect (internal name: Recon1) pseudo-UAM is used by f.e. Time Capsule to keep connections alive gracefully; we should look into supporting it

there are FIXMEs in existing UAM code that alludes to potential openings where to start

this UAM is documented in the AFP Security specification: https://developer.apple.com/library/archive/documentation/Networking/Conceptual/AFP/AFPSecurity/AFPSecurity.html