bmp support for nedmail and marshal (missing from previous post), also, 
nedmail now uses file(1) to guess the extension to add to unknown mimetypes,
(application/octet-stream attachemnts get sensible extensions)

Not entirely happy with this implementation, file(1) has some intelligence,
so does marshal, and now nedmail, page also knows some things, and the plumber
knows others. Shouldn't this magic (sic) be in one place?

-Steve