hdf5_ep

[svn-r5510] Purpose:
    Code cleanup/bug fix

Description:
    The "metadata accumulator" cache in the library (which is designed to catch
    small metadata writes/reads and bundle them together into larger I/O
    buffers) was incorrectly detecting the important case of metadata pieces
    being written sequentially to the file, adjoining but not overlapping.

    Additionally, the metadata accumulator was not being used to cache data
    read in from disk, only caching writes.

Solution:
    Fix accumulator to correctly cache adjoining metadata writes and also to
    cache metadata read from disk.

    Between these two fixes, the number of I/O requests which resulted in actual
    reads/writes to the filesystem dropped from 393 requests to 82 for the
    particular test I was using. :-)

Platforms tested:
    Solaris 2.7 (arabica) w/FORTRAN & FreeBSD 4.5 (sleipnir) w/C++