fix type casting compile warning

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1701 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
move attr.c to attr.m4 to fix type casting compile warning

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1702 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
remove unused variables

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1703 c368ceb8-fd28-0410-a457-e46ee1d7cd4a
when enable-debug, add -g only when it is not presented

git-svn-id: https://svn.mcs.anl.gov/repos/parallel-netcdf/trunk@1704 c368ceb8-fd28-0410-a457-e46ee1d7cd4a