add checking for return error code

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1944 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
do write first, then read, if both write and read present

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1945 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
combine calls to the same if conditions

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1946 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
several error checkings are missing

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1947 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
rename INDEP_COLL_IO to NONBLOCKING_IO to avoid confussion. Also revisit type checking

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1948 c368ceb8-fd28-0410-a457-e46ee1d7cd4a