change connect.socket in poll.socket example from * to localhost

[jcai849]

The poll.socket() example left me with an error at the changed line;
Binding on all endpoints with connect.socket() as per the example yields the following:

> connect.socket(out.socket,"tcp://*:5557")
Invalid argument

With associated errors:

> zmq.errno()
[1] 22
> zmq.strerror()
[1] "Invalid argument"

Specifying "tcp://localhost:5557" as endpoint ensures appropriate connection, and fixes the issue.

[armstrtw]

nice catch. did not raise an error in earlier versions of the core library.