Allow non-local peers to interact with epmd

I am running distributed Erlang applications in the cloud using Docker [1]. To make this work for Erlang, EPMD must allow non-local peers to interact. The peers are non-local because they run in their own containers. An overview of this use-case is described here:

https://github.com/thijsterlouw/docker-research/blob/master/pictures/erlang-docker.png

This patch adds an option "-allow_non_local" to explicitly allow non-local peers. This terminology was previously used in epmd, so I stuck with it. Note that I did not update the ``start_epmd`` function for VXWORKS, since I counted 10 arguments already and didn't really see the need to allocate more.

[1] www.docker.io