Respect svg:font-face-format element.

Call libeot to parse font if value "embedded-opentype" is found.

Change-Id: I03a072fd4db47d151a3934e959ad17c1e24fcf09
Reviewed-on: https://gerrit.libreoffice.org/6144
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>