fix #532 removing unnessary type cast in splitter
(cherry picked from commit f9f9dfbaedf13ab824e61627efc46cec9bfc9b44)
fix #642 Some wrong scrollbars were displayed in the splitter panels.

In these cases, this prevented from scrolling the content panel.
Some miscalculations of the width and height have also been fixed.
The splitter border  width is now accessible from the skinning system (by the new borderWidth property).
(cherry picked from commit 3fb53ec1b36bb665f595a867728328670143e6f5)

Conflicts:
	test/aria/widgets/WidgetsTestSuite.js
patch v1.3.7G