Fix IE8 Editor scrollbars: add doctype on editor's iframe, fixes #16804 !strict

git-svn-id: http://svn.dojotoolkit.org/src/dijit/trunk@30951 560b804f-0ae3-0310-86f3-f6aa0a117693
(cherry picked from commit 34d04841099d28f6de3a25fc6c29dff28accc60f)

Conflicts:
	_editor/RichText.js