Work to fix bug NB#80656.
* src/modest-tny-msg.[ch]:
* Added support for fetching errors in tinymail when we add
attachments. In particular, now we set an error in
copy_mime_stream if it was not successful.
* src/modest-ui-actions.c:
* If creating message has errors because of stream read failures
(i.e. after removing a media or switching down a server in a vfs
stream) we go on but avoid adding the message. We also show an
information banner.
* src/modest-mail-operation.c:
* Manage on message creation the case of an error reading
attachments so that we don't stop processing and show proper
error at the end.
* src/modest-error.h:
* Added new error for file io (it'll happen when we fail to
retrieve an attachment).
pmo-trunk-r4424