* check addition in rev 1.72 of volume_io/Volumes/volumes.c

* rationalize the testing into "testdir/".  I initially put 
  stuff in volume_io/Testing in order to separate the testing of
  minc proper from testing of volume_io.  But some of the "minc"
  utilities (xfmconcat, xfminvert) use volume_io, so there is no
  real separation, it seems.  Might as well move all testing stuff
  to testdir.
