utf-8 fields decoding withing match_field and similar function

[reditigri]

Currently a lot of emails in a lot of languages use encoded header fields as non-latin characters used at To, Cc, Bcc, Subject fields. While server-side IMAP searches usually work smoothly, I expect that match_field and similar functions should have capability to work the same way with header decoding. So, is it worth it to support at least utf-8 encoded string decoding for match_* functions (maybe overloaded version)?