Fix left alignment of native RTL pre-edit text.

Fix left alignment of native RTL pre-edit text.

If there is no committed text in a TextInput or TextEdit determine
if the pre-edit text is right to left before falling back to the
global keyboard settings.

Change-Id: I7e5568e936341602b8faf7be120f9a770c115f48
Task-number: QMLNG-72
Reviewed-by: Michael Brasser
Reviewed-on: http://codereview.qt.nokia.com/4176
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>