add trsock module for greater speeds

[Vizonex]

Decided to screw around with something and In doing so I found an upgrade. I have a exposable Socket CAPI that I found when writing pywepoll and I decided to add that here to see if performance would improve in some areas.

[tarasko]

Hi @Vizonex, it's good to see you here :)

I totally agree it is nice to remove the dependency on asyncio.trsock and have our own copy of TransportSocket.
But for now I would prefer to exclude socket.pxd from this PR.

The thing is, without a clear use-case and benchmark results, these extra 150 lines in socket.pxd is just an additional burden for the project.

The project is already using send/writev/WSASend directly without python layer in transport.pyx.
As for the rest socket methods (getpeername, getsockname, etc), if they ever become a bottleneck their results can always be cached by user from Protocol.connection_made.

Honestly, I'm not sure if TransportSocket should be even cythonized. The code there is rarely used, out of the hot path. Less compilation time, simplified debugging is always good.