Add IAccessible2 table2 implementation.

Add IAccessible2 table2 implementation.

Implement the IAccessible table2 interface for itemviews.
This is simpler than what we have in complexwidgets.
For now it is only used on Linux.

The new table2 interface is ifdef'ed to only be used on X11.
Improve handling of accessible events and clean up.

There are two xfails for the Table and Tree where sibling
navigation is not implemented yet.

Reviewed-by: Gabi
(cherry picked from commit e797ba558dddd45522b5a317316e497e9efc44a8)
(cherry picked from commit eff5ecc5d8f65fa25d6cfd6ed96a9d2a00d0c663)
(cherry picked from commit d29876008fad400bca8d6b37e5d5f61dd1bcb39d)
(cherry picked from commit 2a326fdc8f8bf2bd2c5764394616100906d9db2d)
(cherry picked from commit 9b72e79e20d0d3560e0b064b8b0d75e35feb720e)
(cherry picked from commit 075b0f744363842ed4179c644d933d461389544f)

Change-Id: I654f74991830ae1fc7df7cc91d930390fb88b2a4
Reviewed-on: http://codereview.qt.nokia.com/3274
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@nokia.com>
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>