vfs_fruit: Time Machine/FULLSYNC: add mDNS/DNS-SD advertisement

[Omri Mor]

> afaict the device info advertisement is not required for TM, so we should
> probably keep it out of this patchset.
> 
> -slow

Makes sense; I just wanted to confirm.

What string handling routines does Samba use?
The dkN TXT records need the share name in them (as well as the UUID, but I’ll worry about that after), so I need something like sprintf().
The sys record can be static though.

Samba has, apparently, a concept of service name and volume label; I’m not sure which to use.
lp_servicename(), lp_volume(), or volume_label() (which uses the volume if it exists, else the service name).
Volume is (presumably) set using the `volume` option.
This primarily hinges on what macOS uses for the share name.
In my short testing, it seemed to use the service name—I guess the volume label is something used only by Windows?

Omri