[Kde-bindings] make Qt::Object superclass of rbuic's UI class

[airh2002]

While this week, I have run some stress tests for both with-Qt::Object 
and without-Qt::Object.
I expected with-Qt::Object runs more faultlessly.
But, without-Qt::Object almostly runs and fails a little as same as 
with-Qt::Object. So,

Richard Dale wrote:
> We could change it, but I wonder if it should be an option passed to rbuic4, 
> rather than doing it by default.
>   
I agree this proposal.