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.
2. H5HFstat.c: Since H5HF_space_size() zeroed out fs_size, add "meta_size" to store
free-space size before adding to "heap_size".
3. h5stat_gentest.c: increase # of groups to get "h5stat_newgrat.h5" that contains
indirect block entries in fractal heap.
This is for testing the recursive part of the code in H5HF_man_iblock_size().
4. h5stat_newgrat.h5: the new .h5 file generated by h5stat_gentest.c.
5. h5stat_newgrat.ddl: expected output from new "h5stat_newgrat.h5".
Tested on kagiso, smirom, linew.
