use pnetcdf_libvers variable

Seems silly to have this variable defined but not used, then
re-implement something similar a few lines later

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1895 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
pass correct type to MPI routines

clang type checker finds a few areas where we were passing addresses to
pointers instead of pointers.  Not sure how this passed our tests...

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1896 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
silence uninitialized variable warning

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1897 c368ceb8-fd28-0410-a457-e46ee1d7cd4a