hdf5_ep

[svn-r5393] Purpose:
    New Feature

Description:
    The VFL flush function is called immediately before a file is closed.
    This can cause duplicate syncronization actions to occur, if the VFL
    close function also performs them.

Solution:
    Added 'closing' parameter to VFL 'flush' operation.  This allows the VFL
    flush function to bypass operations that will be duplicated within the VFL
    close function.

    Additionally, use the 'closing' parameter to bypass calls to MPI_File_sync()
    when set.  Since MPI_File_close() also syncronizes the file, this avoids
    the terrible performance hit taken when calling MPI_File_sync() as the file
    is closing.

Platforms tested:
    IRIX64 6.5 (modi4)