Improve error handling for large messages
* src/mail.cpp (add_attachments_o): Move into class and handle error with a message. * src/mail.h: Update accordingly. * src/oomhelp.cpp, src/oomhelp.h (add_oom_attachment): Optionally return the exception description.
This removes the "Sorry attachments cannot be removed" warning
by setting m_disable_att_remove_warning during adding because
Outlook sends an AttachmentRemoved event when an Add fails and
additionally shows the error when the Add in OOM fails in
- GnuPG-Bug-Id: T4731