refactor main.cpp
Merge branch 'master' of https://github.com/minetest/minetest.git
Merge branch 'master' of https://github.com/minetest/minetest.git
Merge branch 'master' of https://github.com/Zeno-/minetest.git
Create CoreSettings and use them for most instance that will improve client performance
Update most time-critical (expensive) functions to use g_core_settings