[1.1.X] Fixed #6918, #12791: If an email message has an encoding, actually use...

[1.1.X] Fixed #6918, #12791: If an email message has an encoding, actually use that encoding to encode body and headers. Thanks for patch with tests oyvind.

Backport of r12683 and r12688 from trunk.



git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12689 bcc190cf-cafb-0310-a4f2-bffc1f526a37