Make faces shading correct for all possible modes.
Skip shading for lightsources and top of the nodes.
Fixes liquid sources and flowing surfaces having different brightness.
Fix mainmenu game initialisation
Merge remote-tracking branch 'minetest/master'

Conflicts:
	builtin/mainmenu/init.lua
Revert "Increase curl_timeout to 59s"

This reverts commit 6547998af87dc4998bb0f08af1042d0117b80a6c.