hdf5_chunking_query_bmr

[svn-r11229] Purpose:
    Big fix

Description:
    A group opened by dereferencing a object reference would not work for
H5Giterate(), due to the local heap & B-tree information not being cached.

Solution:
    Get the local heap & B-tree info & point to that structure instead of
the group entry for the group.

Platforms tested:
    FreeBSD 4.11 (sleipnir)
    Too minor to require h5committest