Broken test now check if headers are correctly encoded.

Broken test now check if headers are correctly encoded.

* 'broken' test, in addition to testing that the mail was
  correctly parsed by email python module, now also test
  that every header can be decoded correctly (that mean
  that for example, a subject header with 8 bits contents
  will be marked as broken.)
git-archimport-id: frederic@jolliton.com--2004-private/mail-filter--main--0.1.2--patch-4