Bug 13661 - We must ignore OpenDoc soft page breaks, they are not manual page breaks.

Cherry-pick from trunk@34703. By jbrefort.

git-svn-id: svn+ssh://svn.abisource.com/svnroot/abiword/branches/ABI-3-0-0-STABLE@34704 bcba8976-2d24-0410-9c9c-aab3bd5fdfd6