Fix Particle errors minetest-mods#81

Unfortunately [fill is only available from v5.8 onwards

ERROR[Main]: generateImage(): baseimg is NULL (attempted to create texture "")
ERROR[Main]: generateImagePart(): baseime == NUL for part_of_name="[colorize:#FB0:255", cancelling.
ERROR[Main]: generateImage(): Failed to generate "[colorize:#FB09:255"
ERROR[Main]: part of texture "^[colorize:#FB0:255"
ERROR[Main]: generateImage(): baseimg is NULL (attempted to create texture "^[colorize:#FB0:255")

mod.conf

@@ -2,3 +2,4 @@ name = nether
 description = Adds a deep underground realm with different mapgen that you can reach with obsidian portals.
 depends = stairs, default
 optional_depends = toolranks, moreblocks, mesecons, loot, dungeon_loot, doc_basics, fire, climate_api, ethereal, xpanes, walls
+min_minetest_version = 5.8

nodes.lua

@@ -668,11 +668,11 @@ local function smash_lava_crust(pos, playsound)
 		maxexptime = 1,
 		minsize = .2,
 		maxsize = .8,
-		texture = "^[colorize:#A00:255",
+		texture = "[fill:1x1:#A00",
 		glow = 8
 	}
 	minetest.add_particlespawner(lava_particlespawn_def)
-	lava_particlespawn_def.texture = "^[colorize:#FB0:255"
+	lava_particlespawn_def.texture = "[fill:1x1:#FB0"
 	lava_particlespawn_def.maxvel.y = 3
 	lava_particlespawn_def.glow = 12
 	minetest.add_particlespawner(lava_particlespawn_def)
@@ -874,11 +874,11 @@ local function fumarole_onTimer(pos, elapsed)
 				maxexptime = 1.4,
 				minsize = .2,
 				maxsize = .8,
-				texture = "^[colorize:#A00:255",
+				texture = "[fill:1x1:#A00",
 				glow = 8
 			}
 			minetest.add_particlespawner(embers_particlespawn_def)
-			embers_particlespawn_def.texture = "^[colorize:#A50:255"
+			embers_particlespawn_def.texture = "[fill:1x1:#A50"
 			embers_particlespawn_def.maxvel.y = 3
 			embers_particlespawn_def.glow = 12
 			minetest.add_particlespawner(embers_particlespawn_def)