Add a tool to adjust the maximum framerate in Krom

I recently ran into an issue with the physics engine causing everything to well fly around in all directions anywhere below 50 fps.

To be able to debug this I used nVidia control panel in my case, but as this requires a restart of Krom it would have been more ideal if I could adjust it on the fly directly within Krom itself.

A tool like this could also be useful when debug common gamecode to make sure you havent left in any code thats assuming a certain framerate (say you forgot to multiply something by delta time).

Start by locating Krom's maximum-framerate handling and the existing entry point for runtime tools. Define the adjustment's runtime interface and verify that changing the maximum framerate takes effect without restarting Krom, including during physics and game-code debugging.

Written by the indexing model from the issue text.