replace use of MPI_LB and MPI_UB by MPI_Type_create_hindexed and MPI_Type_create_resized; add a test program for read/write large variable

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1762 c368ceb8-fd28-0410-a457-e46ee1d7cd4a