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
b8f131dc78