ATW: "bubbles" of missed vsyncs in D3D11 ATW implementation about osvr-rendermanager

[russell-taylor]

My issue relating to missing vsync was one of reporting rather than one of time bubbles. With my testing on the master branch (with only one application with a few settings, and with only one HMD), things were smooth and did not exhibit these bubbles. I did have trouble with the addition of messages causing rendering bubbles, so it is possible that the warnings themselves are contributing. We could consider printing them only once every second or so and reporting summary statistics rather than printing them at every frame skip to see if that fixes the issue -- you could check this by adding a temporary static boolean that stops printing after the first time and see if that improves the judder performance.