bgm模块添加可调节的最大加载数限制，更不容易达到引擎加载音频数上限 close #447

main.lua

@@ -52,6 +52,7 @@ local _LOADTIME_=TIME()
 Z=require'Zframework'
 FONT.load('parts/fonts/proportional.ttf')
 SCR.setSize(1280,720)--Initialize Screen size
+BGM.setMaxSources(5)
 BGM.setChange(function(name)MES.new('music',text.nowPlaying..name,5)end)
 
 table.insert(_LOADTIMELIST_,("Load Zframework: %.3fs"):format(TIME()-_LOADTIME_))