Suspect Windows UDP operations

[Ralith]

The Windows UDP I/O operations that deal with explicit SocketAddrs seem to be missing the WouldBlock handling that their addressless analogs have, and which are presumably necessary for readiness notification to work: https://github.com/tokio-rs/mio/blob/master/src/sys/windows/udp.rs#L76-L86

Additionally, it's odd that connect has that handling, as UDP connectedness is a purely local convenience function that performs no actual I/O whatsoever, and hence is probably incapable of blocking.

[Thomasdezeeuw]

@PerfectLaugh can you look at this?

[PerfectLaugh]

I have to wait for the #1055 land on first since I made changes in udp.rs

[Thomasdezeeuw]

Closed by #1066.