Arabic text is clipped when alignment is not set "right"

Sauer Sebastian comment in bug 217191:

The remaining issue is a Qt bug. Compared to the previous solution we have no
way to work around that Qt bug cause Qt doesn't expose the needed informations
to us[*]. So, this needs to be fixed within Qt scribe (QTextDocument,
QTextLayout and friends). The attached demo-application is a small 70-lines
PyQt python-script that demonstrates the problem in a Qt-only application[**].

[*] We would need the value that is added to QTextLine.naturalTextWidth() if
QTextOption::IncludeTrailingSpaces in the QTextLayout::textOption is set. This
would allow us to to the alignment ourself / adjust the QTextLine's position to
not cutoff right-to-left text.

[**] Please install PyQt (or PySide) and execute the attached main.py. There
are 2 bugs;

1. Switch between "right" and "justify" alignment by pressing the matching
buttons. See that the text is partly cutoff on the right side on "justify"
while it looks fine on "right" alignment. This is the problem we can see with
the attached withArabicText.docx document.

2. Switch again the "right" alignment. Place the text-cursor at the beginning
of the second line (that means right before the "تتيح"). Now press the
space-key ~20 times. Everything looks as expected and the additional spaces are
added to the left while the text stays proper right aligned. No text is
cut-off. Now switch to "justify" alignment and see that the spaces are now
responsible for cutting off the right side of the second line. Text is partly
cutoff now. That text is cutoff on "left", "center" and "justify" alignment
while it's correct with "right" alignment.

We where able to work around the 2th case (that was fixed with commit
3c1e0bdc10) but we have no way to work around the 1st case (cause the Qt-API
doesn't allow so). Also the workaround added for the 2th case is rather dirty
and it's probably in conflict with anything we could try to make the 1st case
less worse.