This was causing deadlocks all over on Windows. Now things seem to be
running smoothly!

This is necessary for URBs which synchronously complete. This is common on
the win32 backend.

This can get out of hand if the client is producing frames faster than our USB device accepts them, leading to large kernel-space queues and high latency. This patch causes intermediate frames to be dropped, but it will always update the device with the latest frame buffer state.

After discussing with Ping, changed the format of the color correction command to use a MIDI-style SysEx command in OPC.

The server now works end-to-end, yay.

Almost fast enough.. just 1.3ms more to shave off per frame.

Originally I wasn't planning on doing this, but since I need to reclaim some RAM anyway, might as well just start hacking out everything we don't need...