in documents, don't change them to wmf and image/x-wmf
silently, resulting for example, dropping or rejecting
modified documents by firewall packet filtering.

Change-Id: I3b8634ae022c7c026b0ed4ebc345c1c3b3f96337
Reviewed-on: https://gerrit.libreoffice.org/56045Reviewed-by: László Németh <nemeth@numbertext.org>
Tested-by: László Németh <nemeth@numbertext.org>