Builtin/../item: Enable tool breaking sounds

If a tool wears out and is destroyed, it's itemstack count
goes to 0, and we can optionally play a breaking sound.

This patch implements playing a breaking sound when this
occurs. Sounds need to be added to the tool itemdef
registration as the sound name string in the .sound.breaks
member.

builtin/game/item.lua

@@ -474,6 +474,9 @@ function core.node_dig(pos, node, digger)
 		-- Wear out tool
 		if not core.setting_getbool("creative_mode") then
 			wielded:add_wear(dp.wear)
+			if wielded:get_count() == 0 and wdef.sound and wdef.sound.breaks then
+				core.sound_play(wdef.sound.breaks, {pos = pos, gain = 1.0})
+			end
 		end
 	end
 	digger:set_wielded_item(wielded)

doc/lua_api.txt

@@ -3606,6 +3606,7 @@ Definition tables
           actual result to client in a short moment.
         ]]
         sound = {
+            breaks = "default_tool_break", -- tools only
             place = --[[<SimpleSoundSpec>]],
         },