Use uint64 on win64 for fd type

[yitzchak]

zmq_poll appears broken on win64 due to the fact that the fd slot in the poll struct is a uint64 on that OS. The most recent version of libzmq uses the type zmq_fd_t to account for this. Unfortunately. there are versions of libzmq around on Windows and elsewhere that don't have this type. Older versions just had a #ifdef directly in the struct definition subsituting the SOCKET type on Windows. To account for this I used a read-time conditional instead.

The original issue is from common-lisp-jupyter, The details are at the very bottom of the issue.

yitzchak/common-lisp-jupyter#65 (comment)

[orivej]

I've looked up that zmq_fd_t was introduced in zeromq/libzmq#3498 and released in 4.3.2. Your change looks good time, will merge soon.

I was writing the bindings based on the documentation, and it still says that zmq_pollitem_t.fd is int, even though it was uintptr on Windows since 2009:
http://api.zeromq.org/master:zmq-poll
https://github.com/zeromq/libzmq/blob/v4.3.4/doc/zmq_poll.txt#L28
zeromq/libzmq@d4fdc26
Would you like to report this issue to libzmq devs?

[yitzchak]

I can do that.

[orivej]

Could you review and test an alternative fix in #35? It allows us to ignore fd field size.