mcl_mapgen_core: Make mcl_mushrooms an optional dependency.

mcl_mushrooms was previously an undeclared dependency of mcl_mapgen_core.
Now it is both optional and declared.

mods/MAPGEN/mcl_mapgen_core/init.lua

@@ -1053,6 +1053,7 @@ local function register_mgv6_decorations()
 		})
 	end
 
+	if minetest.get_modpath("mcl_mushrooms") then
 		local mushrooms = {"mcl_mushrooms:mushroom_red", "mcl_mushrooms:mushroom_brown"}
 		local mseeds = { 7133, 8244 }
 		for m=1, #mushrooms do
@@ -1076,6 +1077,7 @@ local function register_mgv6_decorations()
 				num_spawn_by = 1,
 			})
 		end
+	end
 
 	-- Dead bushes
 	minetest.register_decoration({
@@ -1752,6 +1754,10 @@ end
 -- Generate mushrooms in caves manually.
 -- Minetest's API does not support decorations in caves yet. :-(
 local function generate_underground_mushrooms(minp, maxp, seed)
+	if not minetest.get_modpath("mcl_mushrooms") then
+		return
+	end
+
 	local pr_shroom = PseudoRandom(seed-24359)
 	-- Generate rare underground mushrooms
 	-- TODO: Make them appear in groups, use Perlin noise
@@ -1828,6 +1834,7 @@ local function generate_nether_decorations(minp, maxp, seed)
 
 	-- Mushrooms on netherrack
 	-- Note: Spawned *after* the fire because of light level checks
+	if minetest.get_modpath("mcl_mushrooms") then
 		special_deco(rack, function(bpos)
 			local l = minetest.get_node_light(bpos, 0.5)
 			if bpos.y > mcl_vars.mg_lava_nether_max + 6 and l and l <= 12 and pr_nether:next(1,1000) <= 4 then
@@ -1839,6 +1846,7 @@ local function generate_nether_decorations(minp, maxp, seed)
 				end
 			end
 		end)
+	end
 
 	-- Nether wart on soul sand
 	-- TODO: Spawn in Nether fortresses

mods/MAPGEN/mcl_mapgen_core/mod.conf

@@ -2,4 +2,4 @@ name = mcl_mapgen_core
 author = Wuzzy
 description = The core of the MCL2 mapgen
 depends = mcl_init, mcl_core, biomeinfo, mcl_worlds
-optional_depends = mclx_core, mcl_cocoas, mcl_sponges, mcl_ocean, mcl_stairs, mcl_monster_eggs, mcl_structures, mcl_flowers, mcl_farming
+optional_depends = mclx_core, mcl_cocoas, mcl_sponges, mcl_ocean, mcl_stairs, mcl_monster_eggs, mcl_structures, mcl_flowers, mcl_farming, mcl_mushrooms