BibDocFile: RHEL6 magic bindings support

* Patches the RHEL6/CentOS6 magic bindings module to introduce
  a missing file flag.  (closes #1466)

Reported-by: Theodoropoulos Theodoros <theod@lib.auth.gr>
Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>