netCDF spec says no NC_ERANGE error can occur converting between NC_BYTE and unsigned char

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1804 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
fix NC_NOERR and test code regarding r1804

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1805 c368ceb8-fd28-0410-a457-e46ee1d7cd4a