hdf5_ep

[svn-r5097] Purpose:
    Bug Fix

Description:
    Regression test for following bug:

    The H5Gget_objinfo() function was not setting the 'fileno' field in the
    H5G_stat_t struct passed in.

Solution:
    Added a "file serial number" to each file currently open in the library
    and put that in the 'fileno' field.  If a file is opened twice (with
    H5Fopen) and the VFL driver detects that it is the same file (i.e. the
    two file structures have the same "shared file info" in the library's
    memory structures), they will have the same serial number.

    This serial number has two drawbacks:
        - If a VFL driver doesn't/can't detect that two calls to H5Fopen with
            the same file actually _are_ the same file, each will get a
            different serial number
        - If the same file is closed and re-opened, the serial number will be
            different.

    It is be possible to fix the second drawback for many VFL drivers, but it
    would be a lot of effort and probably isn't worth it until we've got a
    good reason to do it.  Dunno if we'll ever be able to fix the first
    drawback...

Platforms tested:
    FreeBSD 4.5 (sleipnir)
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