Commit da45a0e2 added CSS column-count
property to the exported non-standard MULTICOL element. With this change
we are also able to import multi-column DIVs into multi-column sections.
Now we can change the exported element from MULTICOL into DIV which
actually works in browsers supporting this feature. Importing legacy
MULTICOL elements is still supported.

Change-Id: I55bea40326904de7f137e996a000a7d213fa0593
Reviewed-on: https://gerrit.libreoffice.org/3610Reviewed-by: Tor Lillqvist <tml@iki.fi>
Tested-by: Tor Lillqvist <tml@iki.fi>