Added a relative error formula to deal with floating point uncertainty
in the comparison of floats and double types.
Added new tests for this feature to the file generator program and to
the shell script
1) added a new parameter to the h5diff function diff_array that contains
the beginning position of the hyperslab, so that the total position in
the array is printed correctly when reading by hyperslabs.
2) added a new test to h5diff that reads and diffs by hyperslabs. The
test reads a 1GB dataset, from which a 1KB hyperslab was written with
differences .
3) added the generation of 2 files to the generator program to test the
h5diff hyperslab read.
4) changed the h5diff binary pre-generated file names to be more
descriptive (e.g, instead of file1.h5, made it h5diff_basic1.h5)
5) changed the name of the h5repack options text file to info.h5repack
