vchoi_fork

[svn-r8053] Purpose:
    Bug fix

Description:
    Correct two problems with variable-length datatypes in datasets:
        - When overwriting an entire dataset, writing the fill value to the
            file would be skipped, causing problems for VL datatypes when
            objects in the file had been unlinked (and thus the space in the
            file was not all zeros)
        - When an application has set a fill-value for a dataset and the
            dataset's datatype contained a VL datatype, the library was filling
            space on disk with the memory form of the VL information, instead
            of the disk form.


Platforms tested:
    FreeBSD 4.9 (sleipnir)
    h5committest