Stub code for exploring attachments.

  This updates #186, with a way forward.
  Ignore the new util/attachments file.
  Clean the attachments binary on `make clean`.
  Updated a little.  Still not even remotely functional.

  This updates #186.
  Added stub code for dumping.

  This code is not even remotely ready yet, but it does update #186.
  Updated comments a little.
  updated.
  Use memcpy for the body-extraction.

  Note that this is still bogus.
  Delete the data in the (new) destructor.

  This meant we switched to using CAttachment objects on the heap.
  Updated to correctly set the size of the CAttachment data.

  This was missing.

  Still no closer to working correctly for inline parts, but
 Jeffrey has helped a lot - I'm skipping parts I don't need to
 in the GMIME_IS_PART area..