h4h5tools

This change makes h4toh5 recognize the fill value of HDF-EOS2.

HDF-EOS2 stores a fill value as an attribute, which becomes one HDF4 vdata. It has a predefined naming convention; so, if the HDF-EOS2 field name is SWE_NorthernPentad, the vdata name is _FV_SWE_NorthernPentad. Since h4toh5 finds corresponding HDF-EOS2 entries by their names, _FV_ prefix has prevented h4toh5 from matching HDF-EOS2 attributes from HDF4 vdata objects.

With this fix, h4toh5 checks if the name of an HDF4 object starts with _FV_. If an HDF-EOS2 field whose name is matched after _FV_ prefix, h4toh5 silently skips this conversion because that will be handled by other routines.