Create BNA_UNKOWN of -1 to make clang happy with BNAFeatureType currentFeatureType (#5414)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.11@27710 f0d54148-0727-0410-94bb-9a71ac55c965
nMSLink is always less than a 32-bit unsigned int.  Remove tautology (#5414)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.11@27711 f0d54148-0727-0410-94bb-9a71ac55c965
nPoints and nParts are unsigned.  Comment out tautologies (#5414)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.11@27712 f0d54148-0727-0410-94bb-9a71ac55c965