Hi!
I've noticed that when I replying on emails in some cases I see original email's quote in right encoding, and sometimes non-ascii characters are broken.

So, after some digging I've discovered that if I answer on email with
> Content-Type: text/plain; charset="<charset>"
in headers (i.e. non-multipart), then quote text in messagecomposer window is fine.

But if original email has something like
> Content-Type: multipart/alternative; boundary=<...>
or
> Content-Type: multipart/mixed; boundary="<...>"
in the source, then text in message composer looks like
```
РпиÑÑме Ð¾Ñ Ð¿Ð¾Ð½ÐµÐ´ÐµÐ»Ñник, 21 маÑÑа 2016 г. 12:41:33 NOVT полÑзоваÑÐµÐ»Ñ Alex Domoradov напиÑал:
> ÐÑло Ð±Ñ ÐºÑÑÑо, еÑли Ð±Ñ Ð¼Ð¾Ð¶Ð½Ð¾ бÑло покÑпаÑÑ Ð¾ÑделÑнÑе модÑли, а не веÑÑ
```
(i.e. even messagecomposer's text meaning "On <date> you wrote" is broken).

Reproducible: Always

Steps to Reproduce:
1. receive multipart message with non-ascii text
2. click "reply"


Actual Results:  
non-ascii text is broken

Expected Results:  
all text in right encoding