Revision 2985

* gig.cpp/gig.h: Added new method Sample::VerifyWaveData() which
  allows to check whether a sample had been damaged for some
  reason.
* gigdump tool: added and implemented new parameter "--verify"
  which allows to check the raw wave form data integrity of all
  samples.
* gigdump tool: added and implemented new parameter
  "--rebuild-checksums" which allows to recalculate the CRC32
  checksum of all samples' raw wave data and rebuilding the gig
  file's global checksum table (i.e. in case the file's checksum
  table was damaged).
* Bumped version (4.0.0.svn8).