fix: list MAME's hash, plugins and floppy sounds

The libretro core passes system/mame/{hash,plugins,samples} (retro_init.cpp:111-155). Software lists are required in mamemess, where softlists are on by default. The trees and the 19 floppy samples are collected from libretro/mame at the pin.

bios/Other/mame/plugins/cheat/xml_to_json.lua

@@ -0,0 +1,11 @@
+xml = require("cheat_xml")
+json = dofile("../json/init.lua")
+
+function readAll(file)
+	local f = io.open(file, "rb")
+	local content = f:read("*all")
+	f:close()
+	return content
+end
+
+print(json.stringify(xml.conv_cheat(readAll(arg[1])), {indent = true}))