hdf5_msb

[svn-r4965] Purpose:
    Bug Fix
Description:
    If a non-zero fill-value is used for a chunked dataset, any non-existent
    chunked read with an "all" selection (or a contiguous hyperslab selection)
    will return zero for those instead of the user's fill-value.
Solution:
    Fixed I/O code to pass down fill-value to "optimized" I/O routines, so it
    will be available to fill the user's buffer with.
Platforms tested:
    FreeBSD 4.5 (sleipnir)