many cleanups to fix compiler warnings, streamline iteration over objects
in HDF5 file when opening the file, and generally straightening out the code
to be cleaner and simpler.
Tested on Mac OS/X with gcc 4.8 and OpenMPI (which uses clang).
an unlimited-dimension variable, and different processes don't agree on the
whether to extend the underlying HDF5 dataset, or don't agree on the amount
to extend the dataset.
unlimited dimension hanging. Extending the size of an unlimited
dimension in HDF5 must be a collective operation, so now an error is
returned if trying to extend in independent access mode.
Quincey's bug fixes for parallel build portability, particularly
OpenMPI on MacOS-X.
