hdf5_der

Code clean-up.
Description:
    - Removed function prototypes left in by mistake
    - Moved H5Location::getNumObjs() to class Group because the C
      function in this wrapper only takes a group or file id.
    - Moved H5Object::getNumAttrs to H5Location because the C function
      in this wrapper can also take an attribute id.
    - Misc improvements in comments
Platforms tested:
    Linux/32 2.6 (jam)
    Linux/64 (platypus)
    Darwin (osx1010test)