The old distutils way is not compatible with zc.recipe.egg in develop mode,
because egg_info does not provide any information about such scripts.

This does not increase of any packet because the size of certificate signature
only depends on the size of the certificate key.

With 512-bit hashes, it's still possible to use RSA keys as small as 768 bits.

Generating them takes a lot of time and there's no reason to do this by default.
We keep --dh option in 're6stnet' to not break existing configuration.

And automatic renewal of existing certificates.

UDP protocol is useless if nothing is done to prevent fragmentation.
Otherwise, it is at best unefficient.

There exist routers on the internet that filter fragmented packets with specific
data. This is hard to debug because TCP connections hang randomly when there is
no OpenVPN encryption.

Now, only TCP is enabled by default. A second protocol should be there for
better performance when possible, either existing UDP one (provided it is
guaranteed there is no fragmentation) or something better (GRE ?).

This fixes a regression introduced with new protocol to registry (commit
e24eb3f5), which can't transport None value.

- authenticated communications with registered clients
- XML-RPC is dropped
- multi-threaded server

'/usr/bin/env python' also does not set useful process name for start-stop-daemon

Check for dead tunnels evry 5 seconds instead of waiting for the next tunnel_refresh