Multi-column Ul/Li

[pgundlach]

See #185

This is a small example:

<Layout xmlns="urn:speedata.de:2009/publisher/en"
    xmlns:sd="urn:speedata:2009/publisher/functions/en">

    <Pageformat width="100mm" height="100mm"/>

    <Record element="data">
        <PlaceObject allocate-bottom="1">
            <Textblock columns="2">
                <Ol>
                    <Li><Value>A</Value></Li>
                    <Li><Value>B</Value></Li>
                    <Li><Value>C</Value></Li>
                    <Li><Value>The quick brown fox jumps</Value></Li>
                </Ol>
            </Textblock>
        </PlaceObject>
    </Record>

</Layout>

The last item is created with a hangindent (par.lua#678) which gets converted into a shift in a hbox, which is part of a vbox, therefore the shift is to the right.

Now repacking for the multiple columns puts the hboxes into a hbox (with hpack) and therefore the shift is now "down", leading to an increased depth