Work around dynamic shadows (MT5.5+)

- Disable them by default in SP
- Set time of day to midnight and lock it there

minetest.conf

@@ -1 +1,2 @@
-movement_liquid_sink = 0
+movement_liquid_sink = 0
+enable_dynamic_shadows = false

mods/nc_player_sky/init.lua

@@ -7,6 +7,9 @@ local math_ceil, math_floor, math_log, string_gsub
 
 nodecore.amcoremod()
 
+minetest.settings:set("time_speed", 0)
+minetest.set_timeofday(0)
+
 local basetextures = {}
 for i = 1, 6 do
 	basetextures[i] = "nc_player_sky_box" .. i .. ".png"