Make slimes spawn at night in swamps.

* Adds spawn definitions for large, small and tiny slimes to spawn in
  Swampland and MangroveSwamp biomes when light levels are less than 7.

mods/ENTITIES/mobs_mc/slime+magma_cube.lua

@@ -200,6 +200,10 @@ local cave_biomes = {
 local cave_min = mcl_vars.mg_overworld_min
 local cave_max = water_level - 23
 
+local swampy_biomes = {"Swampland", "MangroveSwamp"}
+local swamp_light_max = 7
+local swamp_min = water_level
+local swamp_max = water_level + 27
 
 mcl_mobs:spawn_specific(
 "mobs_mc:slime_tiny",
@@ -214,6 +218,19 @@ minetest.LIGHT_MAX+1,
 cave_min,
 cave_max)
 
+mcl_mobs:spawn_specific(
+"mobs_mc:slime_tiny",
+"overworld",
+"ground",
+swampy_biomes,
+0,
+swamp_light_max,
+30,
+12000,
+4,
+swamp_min,
+swamp_max)
+
 mcl_mobs:spawn_specific(
 "mobs_mc:slime_small",
 "overworld",
@@ -227,6 +244,19 @@ minetest.LIGHT_MAX+1,
 cave_min,
 cave_max)
 
+mcl_mobs:spawn_specific(
+"mobs_mc:slime_small",
+"overworld",
+"ground",
+swampy_biomes,
+0,
+swamp_light_max,
+30,
+8500,
+4,
+swamp_min,
+swamp_max)
+
 mcl_mobs:spawn_specific(
 "mobs_mc:slime_big",
 "overworld",
@@ -240,6 +270,19 @@ minetest.LIGHT_MAX+1,
 cave_min,
 cave_max)
 
+mcl_mobs:spawn_specific(
+"mobs_mc:slime_big",
+"overworld",
+"ground",
+swampy_biomes,
+0,
+swamp_light_max,
+30,
+10000,
+4,
+swamp_min,
+swamp_max)
+
 -- Magma cube
 local magma_cube_big = {
 	description = S("Magma Cube"),