.m3u support for Mp3Player app

(closes issue #14823)
Reported by: macli
Patches:
      app_mp3.diff1 uploaded by macli (license )
Tested by: macli, dvossel



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@233234 65c4cc65-6c06-0410-ace0-fbb531ad65f3