RCon Observer broken on Windows

[aheadley]

Python on Windows doesn't expose the MSG_WAITALL symbol in the socket module, which is used in the rcon observer. We can either force it by using 0x08 on Windows, or refactor the socket code to work around it.

Also the Windows builders are down, @eminence .

[CounterPillow]

I don't even know whether we need MSG_WAITALL. It was added by me trying to fix a bug, but the bug was actually caused by something different. It worked fine for me before without MSG_WAITALL, but judging by what MSG_WAITALL does, it seems like a good idea to keep it in the code there.

If we get less than the requested amount of bytes, appending them to a buffer and retrying seems like a dirty solution.