[Qt] Build error with building with Qt 5.1
https://bugs.webkit.org/show_bug.cgi?id=112435

Reviewed by Noam Rosenthal.

QAccessibleWidget has moved to private.

.:

* Source/widgetsapi.pri:

Source/WebKit/qt:

* WidgetApi/qwebviewaccessible_p.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145899 268f45cc-cd09-0410-ab3c-d52691b4dbfc