Initialise the base class in the configuration phase, before parsing the configuration.

This scheme prevents that a _free on the final class, results in chaos
because the base is not initialised yet, while an attempt is made to
free it.
Free the virtual server if the configuration fails

In an extremely unlikely case that a configuration of a virtual server
fails we must free what we have just allocated.

The virtual server cannot be freed prior to a succesfull _new,
we may leak memory there, but in that situation we already exit the
server (too).
Merge pull request #1065 from cherokee/wrong_configuration_segv_356

I'm going for this solution, if anyone has a better solution, do propose it.