This changes the BEP protocol to use protocol buffer serialization
instead of XDR, and therefore also the database format. The local
discovery protocol is also updated to be protocol buffer format.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3276
LGTM: AudriusButkevicius
When run without parameters, attempts to listen for local discovery
announcements just like Syncthing, and prints them.
With -send, it also sends fake discovery packets. This can be used on
two or more computers simultaneously to verify that they can see each
other.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/2985