Use ip:port as client identifier

[troglobit]

Currently it's not possible to run an omping server and two clients from same IP. Main problem is, that the client is identified only by IP address and not the traditional IP:PORT tuple.

This means, that rh_list must be changed to a list of server info and a list of clients info. The list of clients info doesn't change much, but list of server info (about clients) must be dynamically expandable. This also means (because of memory reasons) to implement some kind of garbage collector which will free long time unused client info after some period of time (few minutes but should be tunable).

From Trac issue #35, initially targeted at v0.0.5.