[NUT-devel] NUT version bump

[Luca Barbato]

While updating my notes I noticed we are using version 3 to generate
something that does not contain the main_flags.

(Yes somewhere I have patches to support BROADCAST_MODE and I'm thinking
about introducing an unseekable PIPE_MODE dropping syncpoints completely)

I suggest to hold either bump to 4 for the version exposing the
main_flags and use version 5 for futher changes or lump together
main_flags and frame specific data support.

lu