allow Fortran90 collective varn APIs take scalar as in argument buffer

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1820 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
use API/constant names for F90 instead of F77

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1821 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
add two varn test programs

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1822 c368ceb8-fd28-0410-a457-e46ee1d7cd4a