mail: add methods to handle non-ascii chars - headencode, addressencode: encode headers - mimeencode: encode message parts not containing patches - new email config "charsets" Users may configure email.charsets as a list of charsets they consider appropriate for the recipients of their outgoing mails. Conversion is tried in this order: 1. us-ascii (ascii, us-ascii are removed from email.charsets if present) 2. email.charsets (if present) in order given 3. util._fallbackencoding, util._encoding, utf-8 if not already in email.charsets