Fixed h5diff to handle variable-length strings in a compound dataset
correctly. Also variable-length string array in a compound dataset.
Bug #1989.
Description:
Garbage values were displayed when h5diff compared variable-length
strings (or string array) in a compound type dataset.
Tested:
jam (linux32-LE), amani (linux64-LE), heiwa (linuxppc64-BE), tejeda (Mac32)
