add test program varn_int.c

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1783 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
cancel all pending nonblocking requests if an error is detected

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1784 c368ceb8-fd28-0410-a457-e46ee1d7cd4a