vchoi_fork

[svn-r20626] Albert's test on bp reveals that the dumper had assertion failure when it tried to display empty attribute data.  I added 
a check for empty attribute in h5dump.c. I also added a check for empty dataset in tools/lib/h5tools.c.

Tested on jam.  But I tested the same changes in 1.8 on jam, linew, and amani.