Add 'enable-parallel-with-hdf5' option for netcdf

NetCDF library implements parallel I/O through parallel-netcdf (in
classic model) or hdf5 (in netcdf4 model). Because parallel-netcdf
formula is not formally in Homebrew, I add an option as in title for
compiling parallel I/O for netcdf through hdf5.

Signed-off-by: Li Dong <dongli@lasg.iap.ac.cn>