win: fix NODE_NET_SOCKET_READ/WRITE signature

The NODE_NET_SOCKET_READ and NODE_NET_SOCKET_WRITE macros are just
no-ops on Windows, but they used to be defined as taking four parameters
while being called with five arguments. Turn them into variadic macros
to squelch a compiler warning.

PR-URL: https://github.com/iojs/io.js/pull/261


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>