switch to 8-bit email encodings, drop QP

we drop QP encodings except for emails, which are apparently less well supported. it seems everything is *mostly* 8-bit clean these days, and our QP routines were causing problems with emails that had "ellipsis" (`U+2026 HORIZONTAL ELLIPSIS`) or "apostrophe" (U+2019 RIGHT SINGLE QUOTATION MARK) - not even multilingual emails, but just smartypants boys. so ditch QP completely - it makes the raw emails way more readable and fixes display, at least in my tests in mutt.