Bug 588237, patch 2:  Fix comment that is now incorrect due to work in bug 563584 or followups.  r=roc
Bug 588237, patch 4:  Pull pushed floats back from the next-in-flow at the start of reflow.  r=roc
Bug 588237, patch 5:  remove the optimization of skipping FlowAndPlaceFloat for some pushed floats, simply because the optimization looks fishy to me.  r=roc
Add crashtest for bug 621424 / bug 588237.