Re-do text rendering to use stb_truetype so it's portable to linux
Handle mismatched swapchain & window sizes

* The debug text used to render at swapchain dimensions, but that could
  make it unreadable if the window was significantly different, so apply a
  scaling factor to account for it.
Better handling of NaN/inf in range histogram

* This is the proper fix for 87bcde1c which is also more explicit about
  what is going wrong. Thanks to the anonymous user who mentioned that they
  clicked auto-fit before hitting the range histogram crash, which got me
  on the right path to track down the exception!