Add Ultra low latency option

[developomp]

On Windows, we can set low latency mode to "Ultra" to get the lowest amount of render queue latency at a driver level.

... we’re introducing a new Ultra-Low Latency Mode that enables ‘just in time’ frame scheduling, submitting frames to be rendered just before the GPU needs them ...

from https://www.nvidia.com/en-us/geforce/news/gfecnt/gamescom-2019-game-ready-driver/

On Linux, however, the best thing we can do is to set __GL_MaxFramesAllowed=1 which is only equivalent to "Low Latency: on" on Windows.

Bringing this feature to Linux would greatly improve its viability as a competitive gaming platform.

[duckydude61]

where do i even put __GL_MaxFramesAllowed=1?

[edisionnano]

/etc/environment

[Freddycat]

I really hope this gains more traction, this should really be a thing on linux!