Add workaround for MUAs that don't handle UTF-8
Some MUAs seem to send UTF-8 in headers (e.g.: Subject) as is instead of escaping it using RFC2047. Those usually get mangled somewhere on the way by the MTA/MDA and we end up with something escaped with 'unknown-8bit' encoding. Python raises an exception if we ever try to parse that, so it's better to at least try to decode it as UTF-8. Fixes: #43Signed-off-by:Arkadiusz Hiler <arkadiusz.hiler@intel.com>