Remove "new global color correction settings" log message

This is way too verbose
Add a received-keyframe performance counter
Document new performance counter
Benchmark: Add a silly throughput measurement tool

This tests the firmware with a busy USB stack, and measures how busy we're keeping it. By virtue of this being a stupid blocking USB client it won't actually be that busy, but this is a baseline at least.
We can go a tiny bit faster without this FLEXRAM_DATA in the USB driver
fcserver: Limit the number of frames to queue as USB transactions

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.
Let's call the current in-development firmware 1.06
waves: Status text, frame rate limit
firmware: Use multiple variants of the inner loop

Now the firmware config flags actually select between several different inner-loops. This will be useful in the future if we want to support different configurations with runtime config options, and right now it's useful for side-by-side comparisons with the various config options.
New color-correction curve function, with a linear section to reduce flicker

This is a big improvement in dithering quality: Near zero, where we have the most problem with visible flicker, this uses a linear curve instead of the usual nonlinear curve.