Default: Add water footstep sounds

Plus one silent sound to break repetition 'default_water_footstep.4.ogg'.

mods/default/README.txt

@@ -249,3 +249,11 @@ Metal sounds:
 
 Tool breaking sounds added by sofar: CC-BY-3.0
   default_tool_breaks.* - http://www.freesound.org/people/HerbertBoland/sounds/33206/
+
+AGFX
+https://www.freesound.org/people/AGFX/
+(CC BY 3.0):
+  default_water_footstep.1.ogg
+  default_water_footstep.2.ogg
+  default_water_footstep.3.ogg
+(default_water_footstep.4.ogg is silent)

mods/default/functions.lua

@@ -109,6 +109,14 @@ function default.node_sound_metal_defaults(table)
 	return table
 end
 
+function default.node_sound_water_defaults(table)
+	table = table or {}
+	table.footstep = table.footstep or
+			{name = "default_water_footstep", gain = 0.2}
+	default.node_sound_defaults(table)
+	return table
+end
+
 --
 -- Lavacooling
 --

mods/default/nodes.lua

@@ -1350,6 +1350,7 @@ minetest.register_node("default:water_source", {
 	liquid_viscosity = 1,
 	post_effect_color = {a = 103, r = 30, g = 60, b = 90},
 	groups = {water = 3, liquid = 3, puts_out_fire = 1, cools_lava = 1},
+	sounds = default.node_sound_water_defaults(),
 })
 
 minetest.register_node("default:water_flowing", {
@@ -1395,6 +1396,7 @@ minetest.register_node("default:water_flowing", {
 	post_effect_color = {a = 103, r = 30, g = 60, b = 90},
 	groups = {water = 3, liquid = 3, puts_out_fire = 1,
 		not_in_creative_inventory = 1, cools_lava = 1},
+	sounds = default.node_sound_water_defaults(),
 })
 
 
@@ -1441,6 +1443,7 @@ minetest.register_node("default:river_water_source", {
 	liquid_range = 2,
 	post_effect_color = {a = 103, r = 30, g = 76, b = 90},
 	groups = {water = 3, liquid = 3, puts_out_fire = 1, cools_lava = 1},
+	sounds = default.node_sound_water_defaults(),
 })
 
 minetest.register_node("default:river_water_flowing", {
@@ -1488,6 +1491,7 @@ minetest.register_node("default:river_water_flowing", {
 	post_effect_color = {a = 103, r = 30, g = 76, b = 90},
 	groups = {water = 3, liquid = 3, puts_out_fire = 1,
 		not_in_creative_inventory = 1, cools_lava = 1},
+	sounds = default.node_sound_water_defaults(),
 })