mailutils: better email header type detection
mailutils: better email header type detection

* Fixes an issue where Unicode strings were split by commas in the
  email. (PR #2713)

Reported-by: Thorsten Schwander <93f11332782bd01ce84ef8c1f78f004bf923d704@gmail.com>
Signed-off-by: Dimitrios Semitsoglou-Tsiapos <6a6862363aaa6e93bbf0fa721048d2ca97773c19@cern.ch>
Reviewed-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio,tiborsimko/invenio