Various fixes and first iteration of 'table flow around floating boxes' code.
Inline-block spans in a line now have a minimum height (height value is taken from the enclosing line).
Inline-block spans no longer have the width of the containing block for the purpose of line layout. Nested inline blocks call layout before the unbreakable metrics of the enclosing line are calculated.
Changed overflow:hidden blocks to take into account floating areas.