made the pit plasma abm much more selective to reduce cpu load

df_underworld_items/dependencies.lua

@@ -0,0 +1,10 @@
+df_underworld_items.abm_neighbors = {}
+
+-- common nodes that can be found next to pit plasma, triggering matter degradation
+-- don't trigger on air, that's for sparkle generation
+df_underworld_items.abm_neighbors.pit_plasma = {"group:stone", "df_underworld_items:glow_amethyst", "group:lava", "group:water"}
+
+-- This stuff should only be used during initialization
+minetest.after(0, function()
+	df_underworld_items.node_name = nil
+end)