This commit makes listener wrapper public. It also switching the default
conversion of TextBox.addChangeListener from a custom addDomHandler
solution to TextBox.addValueChangeHandler, details can be found at http://gwt-code-reviews.appspot.com/2207
Review by:jlabanca

git-svn-id: https://google-web-toolkit.googlecode.com/svn/releases/1.6@4495 8db76d5a-ed1c-0410-87a9-c151d255dfc7