hdf5

[svn-r15886] Purpose: Close bug 1332

Description: Improved external link traversal of h5dump.  h5dump will now
    properly avoid all cycles, even those spanning multiple files.  Improvement
    to the output of committed datatypes.  Committed datatypes are now checked
    for uniqueness (like other objects).  Tests added for these cases.

Tested: kagiso, linew, smirom (h5committest)