Thanks Matias Bordese. (a few modifications of my own)

  in a `with` statement.  Contributed by Giampaolo Rodola.

The fix is to charset.py, which was not doing the encoding to the
correct output character set when doing a body_encode for either
the shift-jis or euc-jp charsets.  There's also a fix for handling
a bytes input in encoders.py.

Patch by Michael Henry, comment changes by me.

Patch by Denver Coneybeare at the PyCon 2011 Sprints.

when test_subprocess was run.

When a header was long enough to need to be split across lines, the
input charset name was used instead of the output charset name in
the encoded words.  This make a difference only for the two charsets
above.