[PATCH v2] emacs: Allow part preferences to depend on message content.

[David Bremner]

David Edmondson <dme at dme.org> writes:

> Currently the preference for which sub-part of a multipart/alternative
> part is shown is global. Allow to the user to override the settings on a
> per-message basis by providing the ability to call a function that has
> access to the message to return the discouraged type list.

This patch looks fine, but it needs a smarter monkey than me to rebase
it.

d