- Improved the implementation of  memory-side hyperslab when writing
  data by taking into account if the selected data is contiguous
  and starting memory offset.
- Fixed various hyperslab and point tests.
- Implemented a test in which the memory-side hyperslab is
  non-contiguous in memory.
- Implemented a test in which the memory-side hyperslab is
  contiguous in memory but with a non-zero offset in memory.

- Implement the assumption that any point selection is non-contiguous
  in memory in both RV_dataspace_selection_is_contiguous() and
  RV_convert_start_to_offset() function.

- The function RV_dataspace_is_contiguous() will return
  a non-regular hyperslab as non-contiguous in memory.
- Generalized the function RV_convert_start_to_offset() such
  it works for both regular and non-regular hyperslab.
- For completeness handle the other selection types explicitly
  in the function RV_dataspace_is_contiguous() and
  RV_convert_start_to_offset().