Changes

Further testing is needed, but on multi-monitor setups on Windows using the GL driver, it appears RetroArch will only sync smoothly when outputting to the Windows-designated primary monitor. Outputting to a secondary monitor will often result in occasional stutter, even in exclusive fullscreen and after accurate refresh rate estimation, [https://mollyrocket.com/casey/blog_0032.html possibly due to a WGL oversight]. Short of switching primary and secondary designations prior to opening RetroArch, increasing audio latency and/or using only audio video sync seems to help mitigate this to an extent. Switching to either the D3D or Vulkan (if available) driver appears to eliminate this problem completely.