CAddrMan: stochastic address manager

Design goals:
 * Only keep a limited number of addresses around, so that addr.dat does not grow without bound.
 * Keep the address tables in-memory, and occasionally write the table to addr.dat.
 * Make sure no (localized) attacker can fill the entire table with his nodes/addresses.

See comments in addrman.h for more detailed information.

src/init.cpp

@@ -543,7 +543,7 @@ bool AppInit2(int argc, char* argv[])
             CAddress addr(CService(strAddr, GetDefaultPort(), fAllowDNS));
             addr.nTime = 0; // so it won't relay unless successfully connected
             if (addr.IsValid())
-                AddAddress(addr);
+                addrman.Add(addr, CNetAddr("127.0.0.1"));
         }
     }