More powerful sound data processing functionality for 64bit platforms

[excln]

• The current version does not load all sound data in the memory because of capacity restriction.
  • So waveform drawing is performed with cache, which contains complicated asynchronous processing and possibly a lot of bugs.
  • Sound note and channel previewing makes disk I/O.
  • The mixed sound data of a whole song is cached (called master cache), which is updated incrementally when sound notes are edited.
• For 64bit platforms, more powerful and smooth sound data processing will be possible if all sound data is loaded in the memory.
  • For example, flexible multi-channel previewing will be possible.
  • All kinds of previews will not make disk I/O.