[shapelib] what format to return null values from character fields

[Rob Cairns]

Thanks for the advice Frank. As you say the problem is a notional rather 
than programming issue. I initially thought that we should standardise on 
dBase specifications, but on reflection think its better to go with ESRI 
specifications because the dbf table is really part of a composite 
shapefile. There is an article at 
 http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.article  
Show&d=18868 which seems to suggest that a null value in a number field 
should be returned as VT_NULL while a null value in a string field should 
be returned as an empty string "".
Best Regards
Rob