Working code.

  This code successfully handles the cases that used to be handled,
 and the new case - if/when this code is ported we'll be able to
 update #186.
  Removed redundency in attachment handling.

  This update introduces the new `CAttachment` class, which is
 used to store details about every attachment which is present
 in each mail.

  Attachments now cover both "traditional attachment", and
 "inline parts".

  Correctly handling the display of inline parts closes #186.

  (However this update might confuse people, because it will
 show more details than it used to.  Remember you can toggle
 the display of attachment names via `show_attachments`.)
  Minor comment updates.
  Remove any corefile when running `make clean`.

  Not that we've ever written segfaulting code ;)
  Added note to switch implementation.
  New primitive "attachment".

  Returns the body of the attachment with offset N.

  Added test-code in `lumail.lua` to display the contents via
 `show_text`, which is neat.
  Fixed style.  Removed trailing semi-colon
  Updated the get_attachment method to return the object.

  This allows us to pass the binary data through to Lua without
 losing anything in a middle-step conversion to UTFString.
  Correctly bounds-check attachment access.

  Because the counting starts from zero we need to test for
 `>= m_attachments.size` rather than just `> m_attachments.size()`.
Refactor headers to use #pragma once rather than
Merge pull request #198 from torstehu/pragma-once-refactor

Refactor headers to use #pragma once rather than #include guards.

I'm not hugely sold on the benefits, but since you've taken the time to contribute, and it continues to build, why not?  ;)
  Comment update on the `force` flag.
  Completion works on any part of the token.

  The lua `on_complete` function didn't work the same
 way as the others - with on_complete returning "Steve Kemp"
 I'd expect to be able to enter "Kemp[TAB]", but this failed,
 and only did prefix-matching (e.g. "Steve[TAB]".)
  Rework argument-picking.

  This should update #199.