hdf5_msb

[svn-r22373] Purpose: 
  Fix h5repacktst (test file generating binary) to address HDFFV-8016  h5repacktst failed in AIX 32bit mode

Description:
  Segmentation fault occurred when h5repacktst try to generate a dataset when
  system memory is limited to 256MB. 
  Add error handling to display apporiate message to exit and adjust the test 
  dataset according to the original size which didn't causing out of memory.

Tested:  test was done by limit memory in csh.
jam (linux32-LE), koala (linux64-LE), ostrich (linuxppc64-BE)