Revision 3481

* gig.h, gig.cpp: Added File::GetRiffFile() method.
* DLS.h, DLS.cpp: Added File::GetRiffFile() method.
* sf2.h, sf2.cpp: Added Sample::GetFile() and
  File::GetRiffFile() methods.
* RIFF.h, RIFF.cpp: Added a 2nd (overridden)
  progress_t::subdivide() method which allows a more
  fine graded control into which portions the subtasks
  are divided to.
* RIFF Fix: API doc comment for Chunk::GetFilePos() was
  completely wrong.
* Bumped version (4.1.0.svn14).