PIVOT-905:  Address two outstanding issues with the workaround for painting
problems during scrolling:
1) The Javadoc for Viewport "repaintAllViewport" property is backwards, and
   lacks some detail.
2) There is no code to implement this workaround for horizontal scrolling
   (as there is for vertical scroll).

This is a merge of revision 1479613 from branches/2.0.x to trunk.


git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1487512 13f79535-47bb-0310-9956-ffa450edef68