Fixes Issue #1070.
Makes right-hand cell greedy when the left content is made narrower.
An onLoad has also been added to the HorizontalSplitPanel so that
initial and reattached splitting works properly. Added code to
recognize special case of setSplitPosition being set with a percentage.

Patch by: bobv, knorton
Review by: knorton



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1125 8db76d5a-ed1c-0410-87a9-c151d255dfc7