hdf5_ep

[svn-r18820] Bug fix: 
    Fixed a bug (1822) in the H5DSdetach_scale function when 0 bytes
    were allocated after the last reference to a dim. scale
    was removed from the list of references in a VL element of the
    DIMENSION_LIST attribute; modified the function to comply
    with the Spec: DIMENSION_LIST attribute is deleted now when no
    dimension scales left attached.

Platforms tested: jam with electric fence, amani amd linew