Map file columns does not work for CCK fields

If you select "First row contains column names" (default) the fields are not automatically mapped if they are CCK fields. Ordinarily this would not be worth bothering about but I had a content type with 40+ fields so I found this shortcoming annoying.

Here is a patch that automatically matches the field names in the CSV to content type's field names.
The first row of each column must be the machine name of the cck field. eg. field_valid_until etc.