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/makefile.linux-mingw

@@ -45,6 +45,7 @@ HEADERS = $(wildcard *.h)
 OBJS= \
     obj/checkpoints.o \
     obj/netbase.o \
+    obj/addrman.o \
     obj/crypter.o \
     obj/key.o \
     obj/db.o \