[PATCH v8 1/8] emacs: Rework crypto switch toggle.

[Austin Clements]

Quoth David Edmondson on Feb 08 at  8:02 am:
> Re-work the existing crypto switch toggle to be based on a persistant
> buffer-local variable.
> 
> To allow this, modify `notmuch-show-refresh-view' to erase and re-draw
> in the current buffer rather than killing the current buffer and
> creating a new one. (This will also allow more per-buffer behaviour in
> future patches.)
> 
> Add a binding ('$') to toggle crypto processing of the current buffer
> and remove the prefix argument approach that achieves a similar
> result.

LGTM.