hdf5_ep

[svn-r15136] Purpose:
bug fixes.

Description:
Added code to create an empty hdf5 (named h5diff_empty.h5) in order to test
if h5diff compares correctly an empty hdf5 vs. a non-empty one.

Tested:
Tested in kagiso of h5diffgentest itself.
Verified by h5dump that h5diff_empty.h5 was indeed empty.
Then "h5diff h5diff_empty.h5 h5diff_basic1.h5" returned 0 (should have
returned non-zero).