Documentation

Set up and start the main loop providing input and output.

Apparently some SDL backends are not thread-safe (https://wiki.libsdl.org/FAQDevelopment; "this should only be run in the thread that initialized the video subsystem, and for extra safety, you should consider only doing those things on the main thread in any case") so we stick to a single bound thread (but not to the main thread; enough is enough and at least in the case of OpenGL all bound threads are supposed to be as good as the main thread).

The name of the frontend.