hdf5

[svn-r13757] 
h5repack and h5diff hyperslab I/O

changed the limit on which  hyperslab I/O is done from 1GB to 128MB

h5repack currently tests this feature by defining a dataset with dimensions of 128MB + 1byte (the datum being 1 byte integer), in which a 1Kb hyperslab was written.

tested: linux
there were some errors in running the tests, but these were in the library, due to a recent check-in that will be fixed shortly (at least we hope :-) )