[neon] building test branches

[Jonathan Riddell]

Watching the video of my talk at FOSDEM (I'm not vain, it's for
professional review) Will asked an interesting question if someone
wants to build a test branch they just wrote a patch for could Neon
make packages of that for people to test with.  I said not currently
vaguely near to that but it might be an interesting idea in future so
posting it here as an aide memoir.

Jonathan