Small improvement on clouds rendering performance

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

Split up ModApiMapgen::l_register_decoration()
Define and make use of CONTAINS() and ARRLEN() macros

Also add a menuheader, menusplash, menufooter_clouds, and allow HD menu footers.
And finally don't git-ignore textures/base/.

Clean and optimize clouds.cpp enough to not really contain any of the small amount of non-LGPLv2/later code left

Added an experimental "far view" thing. Doesn't work exactly like it should and not suitable for real use yet, and might never be.