add collective var1 APIs

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1872 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
first cut of bput_varn API family

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1873 c368ceb8-fd28-0410-a457-e46ee1d7cd4a