Connection initialized _map as a dict containing a single entry
mapping the connection's fileno to the connection.  That was a misuse
of the _map variable, which is also used by the asyncore.dispatcher
base class to indicate whether the dispatcher users the default
socket_map or a custom socket_map.  A recent change to asyncore caused
it to use _map in its add_channel() and del_channel() methods, which
presumes to be a bug fix (may get ported to 2.3).  That causes our
dubious use of _map to be a problem, because we also put the
Connections in the global socket_map.  The new asyncore won't remove
it from the global socket map, because it has a custom _map.

Also change a bunch of 0/1s to False/Trues.