Summary: when using h5diff to compare the results of h5repack (or other tools that copy one HDF5 file to another), a new option is needed to allow h5diff to make an "absolute" comparison of the 2 files. This is the "contents" mode explained in the usage below.
If this mode is present, objects in both files must match (must be exactly the same). If this does not happen, the tool returns an error code of 1 (instead of the success code of 0)
Changes to the h5repack test script: the call to h5diff was changed to include -c (maintaining the previous -q).
tested: windows, linux, solaris
