Added 2 new programs:

1- elvindtest: a simple program to verify if a particular
    elvindserver is up or not

2- evproxyplab.cc: evproxy for planetlab nodes. It subscribes
   to the following events:
   host = node's ip addr
   objtype = EVPROXY
   objname = __$nodeid_proxy
   eventtype = UPDATE | CLEAR | RELOAD

   On UPDATE, it adds a new subscription to listen to an
   experiment conveyed by EXPT field of UPDATE message.

   On CLEAR, it removes the subscription for a experiment
   experiment conveyed by EXPT field of CLEAR message.

   On RELOAD, it removes all active experiment subscriptions.

   Also, while it comes up, it sends a RELAOD event to emulab's
   event-server to reload it with all existing experiments:

   host = node's ip addr
   objtype = EVPROXY
   objname = __$nodeid_proxy
   eventtype = RELOAD