hdf5_ep

[svn-r24014] This checkin is a merge of the checkin for h5stat to the trunk (rev #23975-23977) + an additional bug fix--
A) Fix for HDFFV-1238:
   --Add 3 new options to allow users in setting threshold for small groups/datasets/attributes (tools/h5stat/h5stat.c)
   --Generate new test file for testing the new options (tools/h5stat/h5stat_gentest.c)
   --Add tests for the new options (tools/h5stat/testh5stat.sh.in)
   --Update expected output files (tools/h5stat/testfiles/*.ddl)
B) Fix a bug in determining maximum dimension size for 1-D dataset in dataset_stats() (tools/h5stat/h5stat.c)
C) Fix a bug when using opt_arg that is NULL for the new options.