This unifies the settings APIs.
This also unifies the sync and async registration APIs, since the async
registration API did not support adding non-functions to the API table.
Move debug streams to log.cpp|h
Move GUI-related globals to clientlauncher
Move g_settings and g_settings_path to settings.cpp|h
Move g_menuclouds to clouds.cpp|h
Move g_profiler to profiler.cpp|h