Avoid style references on text values

A case where a style reference will break the layout is of text that
belongs to a block parent, which in turn has a text-align css attribute
assigned to it (such as 'center').
Without a reference, the line split function would inadvertently modify
the block style during paragraph rendering

Sample html which causes the layout error:
<h1 style="text-align: center">Some text</h1>