silence compile warnings

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1955 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
rename iscontig_of_ptypes to buftype_is_contig

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1956 c368ceb8-fd28-0410-a457-e46ee1d7cd4a