netcdf-c

1. [NCF-276]/XXI-796914
   Columbia server does not serve up proper
   opendap DDS replies. The Dataset {...} name
   changes depending on if the request has certain
   kinds of constraints.
   Code for a hack was not being used, so restore it.
   The fix is to effectively ignore differences in
   Dataset node names if the code is coming from
   columbia.edu.

2. [NCF-278]
   The ncgen code is improperly typing int64 integer constants
   as uint64.

3. [NCF-279]
   Empty string constants were not being properly
   filled when their target array is length 1 or more.